Please don't comment without knowing the fact my friend, it's embarassing. Aprilia's original plan was to enter MotoGP next year but they decided to use this year to collect as much data as possible to build their prototype bike for 2016. They also want to take advantage of the regulations, not to mention this year will be a transition year for the ECU and also tire manufacturer.
Suzuki on the other hand had started their prototype bike project 2 years ago with RDP doing all the donkey work but they didn't join the race until this year. There is an advantage of doing the race and test at the same time, they will be able to collect more data but the downside is that it might hurt their brand because some people who aren't aware of this fact will think that the bike sucks.
It's not easy to develop a good bike/car, definitely not like building Lego in your bedroom. It takes years to achieve that and there's a possibility that they may never get there like what happened to Toyota F1, BMW F1 and also BMW in WSBK. There will be an engine upgrade for Suzuki in June that will give 10 or more hp, but people like you would probably ask "Why wait until June? And why not 50 more hp?".