If you leave them plugged in, they'll squirt out a little ink to prevent said clogging of the head. This is much more economical than washing dried ink residue out with loads of fresh ink.
I have a Brother with a similar approach. It has ink tanks with huge capacity and it powers up once a day to do something which I presume is keeping the heads clear.
It frightened the crap out of me once but I'm used to it now.
We've had a couple different HP inkjet printers, they would clog all the time when not used frequently. Run the cleaning cycle, still doesn't work, clean the nozzles with steam, repeat next month.
We've had a Brother inkjet, and it has been smooth sailing so far.
Nope, sorry, I'm really never going back to inkjets. I've wasted far too much money on them in the past, but more to the point I've wasted too much energy and time on them.
Across several inkjets over 10+ years, they've all been horrible, and maintenance-heavy - especially when they know you really need to print something!
I've had an Epson ecotank for over a year now, and I've never needed to refill the ink tanks once. I purchased it because our previous inkjet printer's cartridges would run out about once every month or two. The driver software sucks but that is true for all home printers.
One of the big points in favor of laser printers has been that they can be idle for a very long time without problems.