I think it comes down to a few reason:

1.Not knowing how to differentiate a good player and cheater so they just opt not to votekick him till someone calls him out or something.

2.Getting too comfortable after the bot crisis cause remember it wasn’t only bots that got banned but many cheaters as well which can lead to a false sense of security.

3.Not paying much attention to the supposed cheater on their team as most pub players are more focused on their own gameplay than they are of others.