Meh, I often lay my mines and spits.
Mostly the reason is to make things more difficult for the enemy and more advantageous for me/my squad and empire.
Often, very often in fact, I don't lay them to get kills. I put them down as an early warning device (who thinks early warning devices shouldn't be in the game).
Namely, if I think NC might attack Naum via a cave link, I'll often go and lay CE, firstly as a deterrance and secondly as something to generate hotspots (hopefully) that I can respond to.
If you're defending a base, put some at the bd, if it disappears go and find out why and kill the lttle beggar who did it.
Even tho I don't do it for kills I usually end up getting a few.
In short, CE is good, emp is good, it all adds to the gaiety of planetside.