Dont underestimate how many people use and prefer mobile to desktop versions. We made that mistake, too, with our site at the beginning. Nowadays its like 15 : 85 in favour of our mobile version, leading to the fact that we ve shifted development resources from the desktop to the mobile version.
No no, that's not my idea, i mean web version should be release before mobile version, because you can still access the web version via your mobile phone with some browsers like chrome, contrary is not. You cannot use a computer to use mobile applications without emulating applications, which will be more difficult and time consuming. But anyway, the mobile version is still needed

Doesn't it all depend on what the website is about for example? I mean sure in gambling mobile could be something very important, on any news websites or maybe even shopping etc etc mobile is very important, nowadays there are less people spending time in front of a computer and spend more time on their mobile phones so I can understand why mobile is getting bigger and bigger.
However, if you build a website that is like a kongregate game just to give an example, mobile people will play their own games, kongregate people will play on PC (requires flash too) that is just one thing I can think of, there must be a million reasons why one website is mainly PC and not mobile, definitely plausible. Mintdice apparently have a lot of mobile users so I understand why they are moving some sources to mobile.