Why is everyone talking about Consolidating UTXOs lately? Is there a way to check how many UTXO's I have if I'm using a Hardware wallet like Trezor?

I've been hearing a lot about consolidating UTXO's lately. Never really heard much about it before. Why is this suddenly becoming an issue?

Is it true that having a bunch of small UTXO will cost a lot to spend or move in the future? I always thought it didn't matter how many single transactions I had.

And what constitutes a lot?

If I understand correctly, the answer is to consolidate UTXOs. Is there a specific method to do this, or is it just a matter of sending everything to one single address? Is there an app for it?

Also, is there anyway I can see how many UTXO I have in my hardware wallet UI? I use Trezor.

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