I'm not a baccarat expert, but here's my take on it:

Baccarat (big baccarat table) has an aura to it. Often in a separate room with higher limits, though not always. The oversize chips are mostly tradition.

You will sometimes see $20 chips (rather than $25's) in use. This is because the commission for betting/winning on the Banker's hand is 5%. That is, a $20 bet, if it wins, pays out an extra $20, minus 5% (or $1 for every $20 bet). Easier to track & collect the commission in $1 increments. If it were $25, the commission would be $1.25 per $25 bet.

Having said that, there are also casinos that use $25's in the baccarat oversize rack too.

And if they deal baccarat on the smaller size tables (same size as a blackjack table), it seems they just use regular rack chips, not specialty baccarat chips.