I think it also has to do with the total hashrate.

For example I mined 0,05 Ethereum 1 year ago with the Rx480 and it took me longer then a month.
Because The Total hashrate was a lot higher a year ago, so it could be possible now that miners are receiving more ethereum.



But I do think people do it because they actually believe in Ethereum and they wont just quit after one period where the market goes down.