Why there's no Bridge + Neck configuration on strats?

Hey guys, i'm a absolute begginer, got a Yamaha Pacifica (HSS) and while playing and dreaming about future upgrades i noticed that there's no configuration on strats (at least most of them) to use Bridge and Neck pickup at the same time, there's a reason for it?

I'm asking because in a future upgrade i would like to place a mini humbucker on the neck to play with two humbuckers at the same time.

And also... while i was making this post i stsrted thinking... There's a difference on playing different pickups positions but same pickups? (For example putting a mini humbucker on the middle instead of the neck and play Bridge + Middle, it would sound different than Bridge + Neck?...)