I understand - it's hard to subscribe to them all - between subscriptions and requests for donations for causes, a person could end up without a penny to their name. When the time comes for me to retire, I will have to think about priorities.
That being said, subscriptions help finance the on-going digiizing and indexing of records although I think volunteers assist in the indexing. Some indexing can be done with software but even then someone had to write the code.