Two words:
Planned obsolescence.
Musical products are only slightly better made that the average coffe maker or microwave oven and made to take only slightly more abuse.
Here's my take --- If that drum machine is in good shape with a dead display you should be able to fire the current kit's drum sounds from any midi keyboard, providing you are willing to do some casting around to find the channel that the drum machine is recieving on. Start with ch. 10 and you may get lucky right off the bat...