The only reason i can think of to consolidate is because youre concerned about tx fees in the future. Maybe also to clean up a wallet with tons of utxos. Of course if you have a small enough utxo, you may not be able to move it when fees are high. Definite potential privacy concerns to consolidation. Everyone will know those consolidated utxos were controlled by the same person.
Discussion
Since we pay for block space, not the value of the transaction, when you have many utxo inputs for a transaction, that literally adds data to the size of the transaction (multiple inputs is more information to relay than one input, for example), which makes the transaction more expensive overall.