One of my very first jobs in the association world was managing the production of a printed directory, a buyer's guide. Within this buyer's guide was a list of over 500 different "categories" of equipment. And each time the directory was updated, the number of categories expanded (members always had some new super-special category that didn't fit anywhere else). Eventually it got so unwieldy we had to take time to cull the list back to a manageable number.
I see the same thing happening with "demographic" data that many of my clients collect about their members. What started as a short list over time becomes a large and unwieldy list of data points that everyone feels obligated to collect but likely very few are actually using.
The reality is, data accretes. The only way to get rid of it is to proactively clean up on a regular basis.
Look at the data you're collecting. Is that data being actively collected and actively used. If the answer to either of these questions is "no" then you've found data you can get rid of.
Data accretes. You have to proactively keep it manageable or it will overwhelm you.