Well it could make sense since one BFL asic chip for example costs 70$per piece if for example I could combine 10 audio chip at 7$each doing half or 1/3 the MH/s rate of a single bfl asic then It would be profitable buying like 1000 chips (which will lower the per chip price) spending a few more K for the board design and you have almost instantly mh power whenever you want to upgrade you have just to make a new order that will arrive in a mater of days maybe weeks at worse.. no 6-9+ waiting time.
So why not use popcorn instead of an airplane since popcorn is so much cheaper? Because if you want to fly across the country, you want something that was designed to fly across the country.
Obviously you are not so familiar with technology (ofcourse there is no problem with that) you consider audio chips graphic chips asics FPGAs x86 Processors as to be completely different things..
They all have things in common they do binary isntructions... their difference is their efficiency per chip at some instructions etc...
So a more appropriate analogy would be this:
to transfere 10000 kilos of gold from lets say africa to USA what do you prefere? to order some fancy highspeed Jets that will need like 10 hours to do the delivery (which you have to wait a year to get manufactured and be available to you and cost like 10.000.000 usd ) or to use simple propeled one seat planes that will do the job in lets say 20 days but cost in total 5.000.0000 and are available right now.