The staff at vaccination centres are trying to jab a lot of people very quickly. This is a numbers game.
If everyone who turns up wants to argue about the type of vaccine, then demand to be jabbed in the car park and dozen other things, then they will struggle to process anything like the numbers we are told are required to get the country back to normal. My local centre are processing 30 people an hour. Now imagine each of those wants to have a "discussion" about the science. You'd be lucky to do four. That's a difference of over 200 per day in that once small centre. A thousand a week.
Anyone is welcome to refuse a jab and stay at home until things return to normal. Just remember that IMHO opinion*, that means you stay at home forever as there will always be another mutation, another stain. If that suits you, then great.
If you chose to make the decision at the centre, then that's a load of time hard-working staff and volunteers need to spend trying to change your mind - and they will do because they want you to be protected. That stops other people getting their jab and the protection it provides.
Personally, I'll take what's on offer.
*Obviously, I'm no expert, but then I don't think anyone else here is.