It's boring and useless.
Just kidding. There's more to it than that.
It's boring for all involved, it's useless as far as being reliable, and it almost always causes way more problems than the department mitigates or is even possible to mitigate, let alone mediate.
The department could be removed, and there would only be positives to come out of it; no one will be harassed by shitsec, no more loot pinatas, no more arguing space law with admins, and it will increase RP. And I'm sure there are plenty of other positives.
There are no negatives; security rarely has a good member, and they usually aren't listened to, anyway, and gets killed by the other members through negligence, ignorance, etc. Security doesn't, or isn't able to enforce the law to begin with, so removing them isn't a problem. There are usually scientists who end up being security, anyway, and that is all that is really needed for any sort of antag deterrent.
Any significant need for security could be mitigated with ERT use. Minor needs for departmental discipline could be handled by the heads of each department as well as IA.
As far as security players go; there are two main groups. Old veteran players, and the ones who are just starting to pick up the ropes. To the new ones; I'd say potentially being hired as some form of security by the HOP might be fun for you, or perhaps as a bouncer at the bar, if you are disappointed at the prospect of no longer having a security department. For the old ones; I'd say that to keep going back to security to try to make security good/fun again is like going back to an ex-girlfriend that does the thing you like, texting you at 3am, saying she wants to meet up, to do that thing you like, only to remember why you broke up in the first place; before she does the thing you like. It would probably be more enjoyable, less stressful, and provides more benefit to the rest of the crew, to move on to a new department.
Really, when it comes down to it; there isn't really a need or use for security, nor benefit. It might as well be the new xeno-arch. Except for hiding bodies; it's for being a domineering asshole, and looting noobs as an antag. It would be more fun and less stressful for all, to remove security.