If you are talking about dielectric grease, helps stop corrosion, reduces arcing,and great to use on household bulbs, no more potatoes to get out the stuck bases
I notice the fluorescent bulbs use stainless on the bases which keeps things working as opposed to aluminum bases. I have used dielectric grease on the old style auto bulbs. I guess I should probably use it on any style.
I use dielectric grease on every single electrical connection on my cars... once you have a 17 year old vehicle and you need to disconnect something that hasn't been disconnected in that long you'll put it on everything so it doesn't happen again.
I also have aquarium lights (CF) that have a pin base that love to corrode together, the grease makes them easy to pop on and off.
Cons... it's grease, attracts dirt. Don't use so much and it's not a problem.
The yellow earwax snot in GM cars works quite well against corrosion, but the bayonet bulbs (twist & turn) still seem to have their base contacts lose springiness and cause issues. I never have to add more grease, they seem to put in 10x as much as was needed.
On cars? For bulbs and connections this is a great thing.
It keeps water/humidity out This is it's primary benefit. Also, there is some direct corossion protection.