There are a number of reasons, but the one that is most compelling to me is that
we are still in the seventh day of creation. God "rested" in His creation (note, God was not tired, He has placed His presence in His creation, and He remains here.)
Hebrews 4:4-9
For He has said somewhere concerning the seventh day: “And God rested on the seventh day from all His works”; and again in this passage, “They shall not enter My rest.”
Therefore, since it remains for some to enter it, and those who formerly had good news preached to them failed to enter because of disobedience,
He again fixes a certain day, “Today,” saying through David after so long a time just as has been said before,
“Today if you hear His voice,
Do not harden your hearts.” (note, the writer of Hebrews is referencing Psalm 95:7-11)
For if Joshua had given them rest, He would not have spoken of another day after that. So there remains a Sabbath rest for the people of God.