The draws "wore out" or were damaged? There's nothing to wear on them, after all, but they can be damaged, such as by people not disassembling or reassembling correctly. You can also have the timber crack or be compressed due to the draws not seating properly - again, often a product of people messing with them who shouldn't. Not saying that was you of course.
The stocks weren't intended for anyone but armourers to remove, and there are some traps for the unwary or untrained in doing this. Getting the process wrong can cause damage.
On the other hand the but socket arrangement does have advantages. It is easy to provide for different stock lengths for example, and these were provided. It is also very strong, certainly strong enough to buttstroke an enemy without fearing that you'd break it. As well, it allowed better utilisation of stock wood, and allowed replacement only of that part of the stock which needed it on a FTR.