Yes, there is a benefit (assuming the new schedule works for you). Until the schedule change is accepted, the reservation and ticket are not fully updated. Anytime there are schedule change segments in a reservation, customers cannot manage their itinerary online and are unable to do OLCI.

Until the Schedule Change is accepted, the reservation shows too many segments. It shows the original one and the new one, with two different statuses (plus any other valid segments), such as shown below on this Phoenix-Charlotte round trip example:
1. US1234Y10APR PHXCLT WK1 (WK=was confirmed...no longer valid)
2. US2345Y10APR PHXCLT SC1 (SC=Schedule Changed...new segment)
3. US3456Y12APR CLTPHX HK1 (HK=is confirmed)

Clicking the Accept button cleans up the reservation so it shows everything confirmed, like this:
1. US2345Y10APR PHXCLT HK1 (HK=is confirmed)
2. US3456Y12APR CLTPHX HK1 (HK=is confirmed)

It also re-syncs the ticket to the new itinerary, thus allowing OLCI. So, if you want to use OLCI, you need to either click the button or talk to someone. If the itinerary is good for me, I click the button. I often times wait a day or two to do so, to make sure I don't need changes, but I'd much rather click the button than call in (if I like the new flights).