I think another reason some might prefer a streamer is the perception that they're buying a product which has been optimised for one purpose right out the box. There is still a fear among many when you mention 'computer': the room's going to be a plethora of wires, keyboards, monitors, mice, need to buy virus checkers, register software, download updates, oh my goodness a big red X has appeared on screen, what do I do crikey I only wanted to play Lina Zaveroni's Greatest Hits! :O
And if not a fear, a belief that computers are somehow a jack of all trades but master of none unless you have a Masters in computer science. Bits, bytes, bit-perfect rips, hifi audio players, FLACs and ALACs. Blimey where's the big button on the front which says "Rip the CD I've just put in, tag it and store it?"
The (streamer) manufacturers of course love all this and emphasise how streamers are so easy to use, one touch rip, one touch play, does everything for you, all in a box, no nasty Windows/OSX updates, nothing to bite you and no viruses. Then to cinch the deal some of them have spin-doctors who are highly-trained agricultural-grade sewage-spreaders, spewing such odorous claims that rips made by their streamers sound superior to those made by computers, even though it would be probably possible to prove at bit-level that the rips are immaterially different, and maybe even completely identical.