As on person who over a period of a year- visited dozens of churches - found that most church members are friendly
within their church clicks. But visitors - well they seem to be at the bottom of importance. -- Some will say -"but I always shake the hands of vistors during the welcome time of the service. That's just great - but when the service is over - then you ignore the visitors.
Yes, there is plenty of this to be sure (and I have seen it with my own eyes), but there is also a reciprocal side that takes place also, in which new persons, are often also shy, stand offish and isolationist (I started out this way myself, a loner). I am not saying I agree to 'ignore' new persons, far be it, but I am saying is that new people are often 'new'. There ought to be a mutual closing the gap in relationship that begins from day 1 (true), and yet that cannot take place by merely forcing one's self into the life of the new person (meaning, going up to them and saying, "Hi, I'm your new best friend that's going to be all up in your business so that you know that you are loved, and so here's my phone, addresses (phys., and email), gimme yours and I'll be at your house Thursday for Bible study and food, and I'll write by email at least three times a day.") . A slow gradual process of conversation, invitation, etc ought to take place. Some new members are unwilling to open up to a larger body of persons, or 'circle' of people they have not known, until they have watched them, processed the group in the minds, made judgments, etc. Many members of churches are also relatively 'new' themselves and just beginning to open up to the group family and expecting them to initiate more than they can handle is also too much. The real job is to the elders, deacons and their wives and families. They are the ones who ought to visit with. The main body of members may have a few solid faithful individuals or families that can be trusted to help extend a hand to the new coming in, but the rest are usually trying to handle the load of life they already have.
I even find that some long standing semi-members (those who are not yet baptized but keep coming), are many times themselves unwilling to commit to fullness of relationship and knowing of persons. They are the ones who have been approached time and again, and offered friendship, conversation, food, and so forth, and yet they choose to remain just outside, and look 'in the window', rather than to deeply experience. They are often not very conversational, even when many attempts have been tried. It might be due to them not knowing how to have a conversation, or too lazy to put forth the effort. They desire to be carried along, or to merely live vicariously through the crowd. I know of several cases in our own congregation that basically let other do all the talking, and conversation is a one way street.
I think that the main problem more than all these, is with us as individuals. What I mean by this, is that while we are Christian, and we desire a larger body of fellowship, often we are uncommitted or unwilling to commit new persons as permanent people in our daily lives. We see these as 'church people, rather than a good neighbour (close brother) whom we desire to share experiences with daily. We are 'weekend' family, not 'everyday of the week' family. We are comfortable with knowing such persons on Sabbath, or at church gatherings ,like prayer meeting, a potluck, fundraise, etc, but outside of the, we think, "I got enough people in my life at the moment and don't need any more." Self-ishness. We are too busy, too greedy, too exhausted, etc and think, selfishly, What will happen if I let these new people into my life, livingroom, heart, and what will it change for me?" We rarely think, How can I bless them, encourage them, edify them. We think, How can they assist me, or will they be a detriment to me? We are at a constant balance of self preservation (individual) and church preservation (collective). We think so long as the collective looks healthy, do not interfere or get any more involved in my individual wellbeing. It's a wrong mindset and backwards.
Some members also have way too much on their shoulders, due to the lack of others taking anything upon their shoulders and bearing burdens and responsibilities. So the overburdened try to carry one more, and topple several together. Think of an elder, deacon or even faithful member that is already involved with 3,4,5 or more families daily, and they try to take on one more past their temporal, mental, spiritual and physical capacity to endure. It is not that they wanted to fail them, but it came about as a result of the equation itself.
Some new members are unwilling to engage new relationships, responsibilities, etc right away. They need time to heal, and a soft constant gentle approach. Others need emergency spiritual medical attention, others physical, and "clear!" Bzzzzzz. Some need to be wooed over time, and others need to be straight told with urgency (Jude 1:22-23, etc).
Anyways, I think there are several factors that play into new member retention and involvement.