A big driver is undoubtedly cost -- and the cool/fun factor is through the roof -- but I think there's also a separation of concerns, a new level of flexibility, and a (subjective) level of effort in maintenance.
From a cost perspective, a computing unit like the RPi is difficult to beat both in terms of hardware and software.
For those of us, me included, that have to lug our stuff outside, I don't mind having a relatively disposable $35 RPi next to the scope. More specifically, I really don't want to leave a laptop or NUC/PC-stick out in the field for overnight imaging. If the RPi's board or memory card dies, it's a piece of cake to replace and restore. The effort to replace the NUC is generally far greater in both cost and re-setting up software. If I take a trip to a remote dark site, having a redundant RPi and memory card is a no-brainer and is still less costly than a single PC stick.
For those of us lucky enough to have a permanent covered installation, the exposure to humidity and dirt and other things isn't as much of a concern. However, getting the stuff in place to connect disparate pieces of equipment (like dome control, weather cams, etc.) gets much cheaper and, arguably, more reliable using good ol' TCP than stringing together active USB cables or getting a good USB extender device. I wish I was in this position.
In the end, you sum it up neatly as being a choice. For my particular use case, SGP already does way more than I expect to ever take advantage of... except in how I would like to connect to my devices 
.
INDI shows tremendous potential. I just about wet my pants when PixInsight introduced some early modules showcasing INDI functionality. I had my rig outside in the terrible heat and humidity and mosquitoes while I was inside in the A/C, wirelessly slewing all over the sky, plate solving, and snapping images.
Exciting times! And I'd love it if SGP could adopt INDI in the future!