how come simple rockets isn't free?

[Spaceman50]

how come simple rockets isn't free

[Vanamonde]

That would be a question to ask on some Simple Rockets forum, because nobody here is involved with it. 

And so, question moved to the off-topic subforum. 

[Shpaget]

I'd say it has something to do with food, housing and life generally not being free.

[jimmymcgoochie]

Unless you're developing software as a hobby in your free time, it costs money to pay the development team; it also costs money to get it published, host any online servers etc., do marketing and so on. In order to get money to pay for all those costs (and to make more money on top of that a.k.a. profit), the game has to include some form of payment- and buying it up front is still the most common way of doing it.