Is maintaining 30 km/h important? Why not leave a little earlier?

Yeah, the person you replied to thinks of cycling as a sport, not as a form of transportation. That is the sorry state of affairs in North America and Australia.

Edit: I see now that you are in TX, so this isn't news to you.

You guessed wrong! I biked for sport in France and the bay area. But also for commuting in San Francisco (so dangerous), and Palo Alto for many years.

My reaction was to the 50 km/h, as if the person was cycling at that speed. edit: maybe they meant that below 50 years old you don't need gears.

By the way, France has switched to a 30 km/h limits in towns. Pretty nice for cyclists feeling of safety.

Oh, I now see I was not clear. I was indeed talking about age when I said "below 50". Not speed. My bad.

My bad! Yes, I interpreted it as "below 50 years old you don't need gears".

That was my original intention indeed :)

I was explicitly talking about commuting in a small city, where there's a lot of start-and-stop-start bicycling is the "way of life". :-)