I mine because it's cheaper to mine, than to buy.
I mine as a hedge to crypto volatility.
I mine because I get to laugh when [mined]-coin drops 30% and you freak out, but I'm still mining it for a profit.
I mine because of the tax write-offs that come with hardware and depreciation.
I mine because I can point my hashing power at many coins based on what's most profitable.
I mine because you have to sit in front of your screen trading, whereas my rigs are making money while I eat, sleep, laugh or cry. When I'm at a recital, or my kids soccer game; when I'm at their swim-meet, taking a sick day, or double dipping at my day job; when I'm watching Thor Ragnarok with my brother, cuddling with wifey, or having drinks fireside with friends and family -- my rigs are making money.
I mine because it supports decentralized stores of value that are independent of government manipulation.
I mine because blockchain is the future and will lead to transparency and accountability in elections.
I mine because blockchain.
I mine because my kids.
I mine.