Since you only have to do transactions to put a balance on coinbase and then can spend it over multiple transactions, does that help scalability?
Short answer: No.
Coinbase inter-account transaction are not Bitcoin transactions. Those surely could help to reduce on-chain tx volume, but can't be considered as a scalability model.
Are those services good for the ecosystem in total?
Yes. Anything that involves trusting 3rd party gets a lot of hate here, but as long as such services remain optional and you can still transact on-chain - I see no problem.