Of course, because every alt is based off BTC price. If BTC goes to $0 so does every single coin. Until the system changes that is how it will be.

Consider BTC will be 50k by the end of the year, what you're mining will much more.

I will take advantage of the possible wave of used cards that may be coming in a couple months. It will all depend on how BTC does over the next month.

I trade. So mining is a great way to get money into the system anonymously, and with extra fees. So any earnings from mining will be multiplied.

Lastly, it depends how you mine. I'm giving out too much game here, but for example I will not being mining ZEC when the difficulty is over 10 when nicehash is paying x amount. I have 6 equihash coins in my script with over 100 conditions. Constantly tweaking it. Also something fun to do.

I just think a lot of people are pissed they have no gear and right now buying cards is not realistic. At least starting from scratch is not. But for us that have been doing it, we are not stopping. I am still looking for cards. Being pretty stingy at least until I can get a grasp on what is going to happen in the next 30 days. If BTC stays around 12 or under with several more crashes many will get out. But if it hits 15 (unlikely) people will keep mining and more will get into it. And as someone above mentioned, profit is profit. You can think of it is as I am finding a $20 bill on the ground once a day. Or I wake up with a $20 bill next to me. Though I do consider it more as BTC will rise. Nothing is dying.  

The other thing too and the reason I never got into ASIC is because they only have 1 use. Old ASIC are completely worthless. But even a video card that is worthless for mining today, has *some* value for others. Same goes for ram, PSU, boards, etc.