In North America there's more space, and I think pharmacies are larger. The European pharmacies I've seen would have had to ditch 5% of their medications if they wanted to make space for a shelf of tissue boxes.
I'm speaking of Germany, but I think it is similar in other European countries. We consider a pharmacy to solely be a place to get medicine from, which is not allowed to be sold in other kinds of stores. They are usually located in smaller buildings where there is not much space to sell anything else (at least nothing big; most have some non-medicine but body-related products taking little space).
The "pharmacies" that are actually middle-sized grocery stores with a medicine counter used to baffle me a lot for the first times I was in the US. It felt really weird to go there not needing any medicine, just to buy drinks or food.
Indeed, if they had a pharmacy counter, where one could get prescription medicine, they would be pretty close to the American pharmacies. I never thought about that...
I think the reason why they don't is that pharmacies are pretty strictly regulated in Germany. They must be directly owned and supervised by a licensed pharmacist, and a single pharmacist may only own a small number of them (something like 3 or 4, a small number so he actually has a chance of supervising them personally). This prevents "chain pharmacies" from operating here, but it's probably also a huge hurdle when it comes to chain-style drugstores wanting to operate a pharmacy section - I guess the entire drugstore would either have to be owned by a pharmacist in that case, or the pharmacy would have to be operated as a separate entity (with a separate checkout process) inside of the same building, which is something that is pretty frequently seen in German shopping malls or those mall-like sections in front of big grocery superstores where smaller merchants can rent shop space.
Yes we still have independent pharmacies that are medicine only, but a very large portion of them have been superceded by Walgreens and CVS which are 60% pharmacy/health and 40% a convenience store.
It is quite nice to pick up a can of soup and some orange juice while you're buying decongestants and whatever else. This model is better for the rural and spread-out US where everything is so far apart.
But a pharmacy is for medication. Tissues aren't medication, can't be predescribed by a doctor and can't be ingested.
It's also not created by a health company, it's not required to be sterilised, ... In the end, you can even use toilet paper, if you have no tissues and it will make no difference.
In North America there's more space, and I think pharmacies are larger. The European pharmacies I've seen would have had to ditch 5% of their medications if they wanted to make space for a shelf of tissue boxes.