The main issue as I understand it is privacy, and whether or not you want to mix coins from different sources.

Let's say you have some non kyc sats you earned or bought p2p, it would be sensible to keep those utxos separate from your KYC exchange bought stash.

And even if your whole stack is fully KYC from an exchange, the argument for multiple utxos (let's say, low single digits) is that you don't disclose the value of your whole stack to someone who receives a payment from you. Of course, you could improve forward privacy of a single big utxo by using a coinjoin payment - but again, at added cost.

Lots of pros and cons to weigh up!