User Profile Service Application Synchronization DB size

I have a SharePoint instance that is running out of disk space. Doing some poking around, I found that the User Profile Service Application Sync_DB has grown to almost 7GB. So, I ran the following SQL query to get more insight into what is going on:
exec sp_MSforeachtable @command1="EXEC sp_spaceused '?'"
Looking through the results I see that the culprits are as follows:

name	rows	reserved	data	index_size	unused
ObjectsInternal	3156618	2089728 KB	800296 KB	1288776 KB	656 KB
InstanceData	177997	4698144 KB	4697048 KB	296 KB	800 KB

I decided to take a peek inside these tables and it looks like there are thousands of objects created every day. So what are these and do they get cleared out any time?

I found a similar question asked: User Profile Service Application SyncDB Database Size. There is an response that is marked as an answer, but it merely leads us to recommended provisioning sizes of these databases to be medium to large (100GB to 1TB). There is no explanation why. This is quite bogus as I only have 75 profiles.

Argh!

I have posted a followup here: Moving the User Profile Service Application Synchronization Database