1. Conference tourneys is a way for conferences to make money.
2. Sometimes it allows an extra team from a conference that is a bubble team to sneak it’s way into the big dance. Again more money for the conference.
3. It allows teams to get use to the NCAA tourney atmosphere just before the Big Dance.
As far as the selection committee IMO.
The tourneys (at least for major conferences) might as well be played at the beginning of the season and generally don’t count anymore than a regular season game, if that much. Being a “marquee program” seems as important to the selection committee as the regular season record. If 2 teams have similar records, the ”marquee program” will get the higher seed.
IMO a big part of the problem is having tourney games right up to the time the selection committee announces the pairings. I imagine they have to have everything almost finalized by Saturday or earlier.