I also have worked in many many offices where the first aid kit was an empty shell, whether it was attached to the wall or a box in the supply cabinet.

That is, except for one company. They had a huge well equipped first aid cabinet attached to the wall in the shop, and monthly a service restocked whatever had been used or had gone out of date.

I think this is really the only way to be reasonably sure that the kit will have what is needed when it is needed. Problem is getting the boss to understand that it is a cost that the company should pay.