why dont they show the teams banning/picking maps?

they used to why not now?

I suspect that its due to the start of this season when Riot brought in new talent and had them do the vetoes it was awkward as shit. They seemed nervous, stuttered a lot, straight up forgot which teams banned what and what side was chosen, and reback vetoes for confirmation incorrectly, etc. Made things seem really unprofessional, so they likely made the decision to just scrap the segment all together.

Sucks cause i enjoyed those too as it added another layer to the lead up to games, as you could see glimpses into the mentality that teams had going into the match.

save time on broadcast probably, but for the important / tourney matches they're not really competing for airtime

So Riot can hide the script