There's a bunch of answers to this. First, it is popular opinion at efnet that channels are not owned, and therefore, if you lose a channel, you should go make another one. But more and more you see opers killing for takeovers, so why are they helping their channels and not yours. Or worse, they could have it all set up, and some other oper could kill them halfway through because they don't like masskills and it would be all ruined. Or, let's say the masskill goes off, then the channel is opless and generally speaking, chaos begins.
People start massnuking or flooding the channel to clear it out, or just to be annoying.
This one is a bit more complex, but its really a personal call. That one op could be a rampant smurfpup with a penis so tiny he has no choice but to rampantly smurf and synflood anyone that gets in his way. This is popularly known on irc as SPS, or Small Penis Syndrome. In this case, if the oper does help you out, they could end up with their server being downed for a day or two, and it really isn't worth it for your channel, no offense. That's the gist of the information I was trying to get across.