I always felt the same about warming up until I started doing time trials last year, when I discovered going from a poor quality warm up of "I cycled 5 miles about an hour ago" to doing a proper progressive warm up meant that instead of getting into my pacing after 2 miles I was able to hit my target pace earlier at a lower heart rate and was able to still push until the finish.
I'm not saying that you need to do a 20 minute warm up for every run, but it's worth doing before key sessions and races as it will allow you to perform better.
I always felt the same about warming up until I started doing time trials last year, when I discovered going from a poor quality warm up of "I cycled 5 miles about an hour ago" to doing a proper progressive warm up meant that instead of getting into my pacing after 2 miles I was able to hit my target pace earlier at a lower heart rate and was able to still push until the finish.
I'm not saying that you need to do a 20 minute warm up for every run, but it's worth doing before key sessions and races as it will allow you to perform better.