Why are older size clothing and shoes seem so difficult to get hold off /not in the sales

[Woodward23]

My daughter is now going into 10-11 and size 2 shoes and after looking online and in shops today im noticing a real lack of both options avaliable or no sizes available .
I use to love buying in the sale and storing them away untill needed but there just seems nothing avaliable in sales in the higher sizes why is that ? Is there a specific reason

Note we only really have an asda and sainsbury in our town which is mainly where ill get the clothes from

Have you found this the same ?

I'm tiny (due to illness) and buy a lot of my clothes from that size up so maybe they sell out. No idea on the shoes.

because they're popular!