Hmm.. which all are?
Its hardly even a choice. As a consumer myself, anything not free doesn't interest me anymore. Companies are spoiling consumers (including me) silly.
It's hard for me to see how they're anything but a form of unregulated (yet) gambling/exploitation of people vulnerable to gambling.
Who in their right minds think that tens, hundreds of dollars is a good price to pay for virtual gemstones?
At any rate, for others that where unfamiliar with Supercell, I'm assuming parent means the makers of:
https://thinkgaming.com/app-sales-data/1/clash-of-clans/
A somewhat related article:
http://www.theguardian.com/technology/shortcuts/2013/mar/26/...
(And there's of course been a number of articles on "predatory" game design, based around compulsive/addictive behaviour)