In close, family-based communities, the rules for who would be in and out of the community (and assemblies) would have really mattered. Not only was there sin (some sins led to exclusion rather than death), but the way nations had treated the Israelites in the wilderness also came into play.
The Israelites were instructed to never forget how some groups had behaved.
For example, some people could never become part of Israel:
Deuteronomy 23:3-6 No Ammonite or Moabite or any of their descendants for ten generations may be admitted to the assembly of the Lord. These nations did not welcome you with food and water when you came out of Egypt. Instead, they hired Balaam son of Beor from Pethor in distant Aram-naharaim to curse you. … As long as you live, you must never promote the welfare and prosperity of the Ammonites or Moabites.
Some groups just had to wait for a few generations:
Deuteronomy 23:7-8 Do not detest the Edomites or the Egyptians, because the Edomites are your relatives and you lived as foreigners among the Egyptians. The third generation of Edomites and Egyptians may enter the assembly of the Lord.
And some were line up for destruction, because they’d tried to destroy the Israelites, picking off the exhausted as they fell behind as they fled Egypt:
Deuteronomy 25:17-19 Never forget what the Amalekites did to you as you came from Egypt. They attacked you when you were exhausted and weary, and they struck down those who were straggling behind. They had no fear of God. Therefore, when the Lord your God has given you rest from all your enemies in the land he is giving you as a special possession, you must destroy the Amalekites and erase their memory from under heaven. Never forget this!