Why are all popular crypto currencies deflationary? There is a lot of criticsm and debate over whether bitcoins will ultomately fail because of its deflationary nature.

I don't want to debate if that's the case or not and I also understand that the goal of bitcoin was to have a fixed amount of coins so that there is no risk of (hyper)inflation.

What I'm wondering is, would it be technically possible for a crypto currency to have a fixed target inflation rate? For example the european central bank has a target inflation rate of 2% (I think) which is supposed to stimulate growth while at the same time avoiding over-inflation.

So I guess my question boils down to: Why are all popular crypto currencies deflationary? Is it a technical problem that cannot be solved or is there another reason it was designed like this?
There's no technical problem with making an inflationary crypto-currency. For Bitcoin, just changing the block reward schedule would do it. And there do exist crypto-currencies that have perpetual block rewards.

The thing is, the set of people who believe that inflationary currencies are good doesn't significantly overlap the set of people who think that currencies don't need to be managed by central banks. So there's not much of a market for such currencies. It's kind of like a veggie burger with bacon.