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ASIC is too specialized. It will only be good at mining bitcoins. Moore's Law, the new generation of ASIC will wipe out the old ASIC so there is an incentive to race to the top... if you don't make back your investment income in time, the hardware will be rendered useless.
At least for GPU, you can use it on your computer, sell it on ebay to other gamers and join Coinlabs (and others tbd).
So you're not buying ASICs because the ASICs that come out after these will be faster (by how much, I wonder?). So by that logic, I shouldn't buy a new CPU, because the CPUs in 6-12 months will be faster than the one I can buy today....
"Useless" and "outdated" are two different things. My brother's "gaming computer" from 2008 with its e8400 C2D, DDR2 ram, and Geforce 9800GTX may be be "outdated" by being several generations old, but it's not "useless" as it still playses Assassin's Creed and Skyrim just fine (which is all he wants it to do).
We buy what we have available, and we continue to mine on it until it's no longer profitable.