Could this be the reason , It's like 15-20mn to get at least 1 confirmation if I'am correct ?
Anyway the point is that we need some time to get transactions verified , could this actually prevent us from going to mainstream ? I mean if you want to buy something from McDonald are you supposed to wait 15mn while that's the time of your launch break ?
When you are buying parking tickets are you also supposed to wait few minuts ?

It wouldn't make any sense .
Honestly , I'am not even sure what controls the speed of the transactions .
No, this is not preventing us from going mainstream. 10 minutes for getting 1 confirmation or 60 minutes for getting 6 confirmations and being absolutely sure that that you will get your money is not a long time to wait at all.
Services that we are using today are much slower (banks, credit card companies, etc..).
Our problem is trust and user adoption and these 2 absolutely depend on each other. Once we get more trust from the average Joe, our user adoption will skyrocket as well.
You are forgetting the fact we can't have proper user adoption as long as the blocksize problem stays unsolved. If we want mainstream tier volume in Bitcoin will need to solve this first, otherwise the network will collapse due too many people using it at once. So before mainstream step is reached, we need to get the block size increased and we need to start thinking about using LN type of solutions as well.