Because multiple UTXOs can be beneficial in the future where OP may need to spend an entire UTXO without creating change.
Creating multiple UTXOs in the present doesn't provide a benefit compared to creating multiple UTXOs in the future, you're still creating them no matter what. Besides, what are the chances the UTXO sizes he picks today will match the exact value he needs for a purchase made in the future?
Also for privacy reasons, because consolidating them is not a good choice. Don't give me the Wasabi consolidation argument once more. I understand you like it but I don't like it so it's not worth trying to convince me. There is also no need to suggest Wasabi every single time. There are multiple tools for multiple use cases. Using only wasabi products for everything is not a good choice any way you decide to see it.
Why don't you like coinjoins?