Probably because you notice
Probably because you notice it more. Plus, the brain tends to assume to first 2 or 3 remembered examples are good enough to estimate the likelihood of something over time. Heading out of your cave to the watering hole (for our ancestors) - well, whether or not there was a Sabre-tooth tiger waiting, recalling the last 2 or 3 most easily remembered examples is a VERY good strategy. Remembering the relative demographics of the gender of a driver of a particular car over a decade? We have the same brains as our ancestors, so it is pretty much a worthless strategy. Actually, it is a well-documented scientific fact that it’s almost certainly wrong, or at best equivalent to guessing randomly. That’s not a criticism of you or our brains ... it’s just something you need to know before you trust it in certain circumstances. Your gut feeling about the girl you just me at a pub? Unless you have terrible judgement and/or no people skills, go with your gut! Estimating percentages over time? Use the scientific method.