Exactly!
And it also allows for interesting opportunities. I don't mine BTC but I have 5 U2's for shits and giggles hashing away on the blackcoin pool. For the very little $$ they cost its nice to have some SHA hardware available. You never know if something might come along that could make the little bastards profitable.
Exactly x2! Plus most vendors are doing what the computer makers did back in the day, scaling up instead of scaling out. Now folks are selling 1TH units like they used to sell 100GH units, however once you go up to that high of a hashrate the power draw becomes something of an issue. For example, I'm east coast US and my power rate is .15 but w/ delivery and taxes it is closer to .29, so running something at 1KW is insane for me. Plus my rental house has a terrible power scheme (and the owners are assholes and won't consider upgrading), so there isn't a single place that is accessible in the house that I can draw 1KW from a single breaker, meaning I physically cannot run a 1TH unit until 1TH units get much, much lower in their power draw.
USB's, and even Gridseeds, on the other hand, are smaller, lower power draw, more manageable heat-wise, and can easily be swapped to other coins at a whim. Plus, not a single 1TH unit coming out right now is going to ROI per current network increases and those fuckballs at KNC, so the argument "USB won't ROI" can be replaced with "Mining hardware won't ROI" and you're more accurate.
Mining is a shitty place, but some of us like to remain involved.
I have a gridseed (which is 300k\8g) and on night time I always moving it with RPi to the kitchen 
