Older reviews don't always age well
A recent argument I've heard could be considered a predicament of the recent beer boom. Beers that have been around for a decade or more tend to carry more reviews than ones released more recently. This makes sense: when there was a field of 10 IPAs to choose from in your market, you were more likely to be impressed. But just like your teenage taste in movies, new experiences can make revisiting something feel less impressive (Garden State, anyone?), and it's very unlikely that your new views are being reflected in your old reviews.
On the plus side...
The reason why I won't tell anyone to up and delete their BeerAdvocate or RateBeer account is simple: if you're getting serious about beer, writing down tasting notes is the best way to remember the stuff you've tried. Both major rating sites ask you to note the appearance, aroma, and mouthfeel of your brew, which are important qualities that many drinkers leave out when compiling notes and are vital at rounding out your observations. It almost makes it like a beer LiveJournal! Except, you know, without the emo music links and dramatic emoji use (unless you're a really emotional beer reviewer, in which case, no judgment).