It's very very very unlikely to be bad luck, but more the routes and days/times you're flying.

If we suppose 70% of flights leave on time (this is slightly lower than the CWS figure above, but might be a more conservative long term average), then there's a 30% chance that a randomly chosen flight is late to leave. To get this 10 times in a row has a probability of 0.0006%, about 1 in 150,000. Not quite winning the lottery rare, but extremely unlikely. I'd expect it's due to you travelling late in the day, and travelling to congested (European) airports.