Even if you combine them, you might end up paying more for adding another utxo to the transaction than what that particular utxo is worth.

In meat space it's not more expensive to add 10 $1 bills together than spending 1 $10 dollar bill.

But in bitcoin land adding a new utxo increases the size of the transaction therefore increasing the total fees for that transaction. There will be a fee level at which certain utxos will be more expensive to send even if added to a transaction with more utxos