We've had clients who have used those all-in-one software packages, and each time the accounting part of the software was total garbage.
Cornerstone's comment on firms not adapting sounds like my former employer - haven't worked there since summer 2004 but know someone who worked there briefly several years ago. She said nothing has changed - paper files everywhere, no networking of computers, no online document storage, invoicing way behind and still done the same way as in the 90's (preparing time sheets, having to enter the time into the billing software, etc), no online portal, work not getting done until right before the extended due date, etc. Every time I think about it makes me happy that I left after 12.5 years and went on my own.