Well, disk brakes are still largely the preserve of MTBs and a good proportion of those (possibly a majority, but I'm not sure) will use schrader valves. So often, you'd just connect it to your own front wheel...
There does seem to be a widespread obsession with bleeding brakes.
I've been using Hope hydraulic discs since, IIRC, 1999, and the only time I've felt the need to bleed them is when replacing the hoses, wholesale; ie. When the system needs completely refilling. On those rare occasions I just gravity bleed them*.
I've never had to pop out pistons for cleaning. The most I've needed to do is remove the pads and work the pistons in-and-out a little to free them up.
Of course, mine get constantly flushed with liquid mud, which is a surprisingly good lubricant. Perhaps discs used in less extreme conditions build up a different consistency of muck...
*I generally don't even use a hose. Just remove pads, open the nipple, and let the fluid drip onto a strategically positioned rag, which goes in the bin. When complete, rinse the calliper off, replace pads and Robert's yer dad's brother.