According to Google: Two reasons:
1. There are more planes in the air. Therefore even with a constant, or gradually decreasing rate of crashes, statistical chances of there being plane crashes can appear constant.

2. Increased global media coverage and news consumption means that you hear about them more often. Where before you might only have consumed news through the TV, radio and newspaper, today we consume a much higher number of news stories via the internet.

Also There is a shortage of Air Traffic Controllers due to various factors, including reduced budget and the moving of Newark control to Philadelphia.

This is also why a lot of people think that the world is becoming a worse place - they just are exposed to a lot more negative news stories than ever before (because negative and shocking news sells, you'd never see news titles that said: "nothing happened today, and everyone got along just fine")