Do need degassing rasin always or all depend from how big item we do?
On easy composite video with the bonnet rasin wasn't degased so?
Is.always necessary?

Not normally necessary, depends what you are doing. Can help with parts that have details that the fibres just cant get into, as these areas will trap bubbles. Improves the appearance of any bridged areas for the same reason.

For the most part, it complicates the process and you don't need to do it. 

I am a degassing fan as well. On larger infusions I can run the resin so much faster without getting any pinholes, that it is worth it time wise. I also do a lot of closed mould work, for wich degassing is necessary in my opinion.
However, i have to admit that easier parts can be done without degassing. But as I do it for living, I love the extra insurance to always get perfect parts. One tiny pinhole and you have to clearcoat the whole part to get a perfect finish.