Pros
The only real benefits are: 1) The total remuneration package is excellent. Basic pay, car allowance, pension contributions, bonus and 30 days holiday is normally enough to keep people there. 2) Most employees are feckless wasters so it only takes a tiny bit of effort to keep hold of your job and avoid too much negative scrutiny. It is very rare to have to stay beyond 5pm or arrive before 9am and your lunch hour is safe.
Cons
As alluded to above, most employees are either blindingly incompetent or lazy. It is rare to meet anyone of any use and those people are normally so fatigued from having to deal with the pointlessness of most activities that they cease to become effective. If you don't work for IT, forget trying to get anything meaningful done. The bank is swarming with "lifers" who do the same thing every day for 30 years without ever wondering why they are doing it.