One of the reasons for that may be the price: large code changes with multi turn conversation can eat up a lot of tokens, while those tools charge you a flat price per month. Probably many hacks are done under the hood to keep *their* costs low, and the user experiences this as lower quality responses.

Still the "architecture and core libraries" is rather corner case, something at the bottom of their current sales funnel.

also: do you really want to get equivalent of 1 FTE work for 20 USD per month?:)