Have you ever had a chain snap on you? It's not fun. Usually it happens when you're really stepping into it, which makes the results that much worse. Knee to the stem, thigh to the crossbar, usually you go over the bars. If you're lucky, you land on your hands instead of your head. If you're not lucky, it happens when you're trying to sprint through a busy intersection and you get run over by a bus. Either way, it's not much fun. But hey, chains break. It happens.
That said, isn't the chain the last thing you'd want to lighten up on purpose? There was a time not so long ago when BMX chains were judged the same way hip-hop chains were: Heavier was better. There was the KMC 415h (or Kink chain) and the massive Sharp 420—which was better suited for a motorcycle or a garage door opener. Had things continued in that direction, we'd all be riding chains that look something like this (minus the feet):
They didn't continue like that, of course. Gearing dropped, so you didn't need to worry about your 45 bashing into everything anymore. And with chainrings out of harm's way, chains were free to get lighter. People went with traditional KMCs, like 410s, 510s and 710s. But that wasn't good enough. Oh no. Road chains had long used drilled-out pins and hollow plates. Izumi made a hollow-plate BMX/track chain back in the day. Why not do the same with new BMX chains? So KMC introduced the 710sl:
It came in at 365 grams as compared to 420 (!!!) grams for the regular 710 (according to Fat). Not much of a difference—less than two ounces. Of course it comes with enough links to run 48/16, so the weight difference is presumably less if you're running 28/10 or lower. And it, um, looks cool.
There are differences between road and BMX, however. Small as BMX drivetrains are, the chains still take hits every once in a while. And running it on a eight-, nine- or 10-tooth driver places a lot of stress on the chain, even if it doesn't have drilled-out plates and hollow pins. KMC can give you numbers for "pin power" and "breakload" all they want, but those don't take into account bashing a drilled-out link on a rail or ledge and then cranking full-out towards something else.
Look, I appreciate that plenty of people run drilled-out chains, and a majority of them are still very much alive. But of all the things to drill out, the part on your bike that arguably takes the most stress? What's next? Steerer tubes? Pedal spindles? Heck, even the Grim Reaper makes more sense to me than this. There are certain things I'd rather not see drilled out. Chains. Stem bolts. Forks. Anything that, if it snaps, will probably send me to the hospital or the dentist. And even barring injury, I'm not a big fan of liamfahyhamptoning around. So I like my chains like I like my teeth and my Alaskan wildlife preserves—undrilled.
(Of course, seeing that half-link chains have seemed to have more problems with snapping than regular chains, there's no way anyone would come out with a drilled-out halflink chain. Well, no one except KHE. Lovely.)
P.S. Sean Burns only rides Wipperman chains. Their 1G8 is apparently the strongest chain on the market, according to—um, them. This video has nothing to do with chains, but a minute of Sean Burns never hurt anybody. Well, except him.