Welcome Makhshev!
I'm buying mostly because the car that I've had for almost 10 years is just wearing out at 150k miles, and this is a great opportunity to finally have a fun and exciting car to drive. There's only so long you can stand driving what is essentially an econobox (not that I don't love my car, I do! It's just...well, slow). Basically, I needed to buy a car this year and the ST has the features, performance, and looks I'm looking for.
It would be safer to wait, yes. But I don't want to dump thousands of dollars in maintenance costs & new tires this year just to trade it in/sell it anyway.
Yes the first model years can (and do) occasionally have issues. But most of these components have been in use on standard focuses for a while now. The big question in my mind though is engine longevity, although the ecoboost line of engines have been among the most reliable and efficient engines Ford has ever produced.