WHY TIME feels like it passes quicker as you get older.

Perhaps, but I have another theory that seems plausible to me, though I'm no expert: as years pass, every day is proportionally bigger as compared with the expected time you've got left. For example, when you're 10, one year is only 1/70th of the time you have left (assuming an perceived life expectancy of 80 years, year more, year less). When it passes it's a relatively small piece of time. But when you're 50, 1 year is 1/3oth so, being a bigger chunk passing, it seems much faster.

I think this is plausible because it works for vacations too; for example, that'd be why you feel the 2nd of a two-week vacation going faster than the 1st one. You may say my theory works only when the duration is determined 100%, and lifespan is not determined that way. But —accidents or illnesses notwithstanding— what counts for this is perception, and we generally perceive we have a life expectancy of 80 years give or take, and we tend to live accordingly.