A few still exist in certain states, though their number has significantly declined over the last two decades.
I'm sure there were a decent number of them in ME who voted for Biden and Collins, to "keep a check on him".
In terms of Biden/Collins voters (and this may also apply to some other contests, such as Trump/Bullock 2016 voters), I think a greater reason for such ticket splitting is not "check and balance," but rather downballot incumbents running for reelection and sufficiently localizing their races & retaining their popularity to win over many ticket-splitters (Indeed, newspaper reports from Maine in 2020 indicated that many Biden/Collins voters were turned off by the campaign tactics of Collins' challenger; exit polls showed that 23% of Biden voters viewed Gideon unfavorably, and 18% of Biden voters voted for Collins.).
