Well that's part of the problem... their size. You can go over to your local walmart and buy a fridge no problem... but try buying 5 from the same store.. ok, they might find some at neighbor stores for you. Now walk in and say you need 10,000 and see what happens
Now add in the logistics that your rooms are 'in use' all the time and you are trying to do this with minimal disruption to your guests.
It all sounds 'easy' when you are doing this in small volumes.. but doing it across many thousands of rooms.. everything scales up and your old methods typically no longer work.
Just think... 'where do I put 5,000 refridgerators waiting to be installed?' or 'where do I put the old ones?'
We also don't know if they are making any modifications to the furniture to accommodate the new ones, etc.