You could describe almost any business with a snarky remark like that. Github: basically re-invented your sysadmin putting up a CVS server, over the internet; Stripe: basically re-invented what a bank used to do, over the internet.

Anyway, this is one of those things that works much much better on the internet. In the bad old days, a travel agent was the only option for booking flights and trips. Now that you can do it all over the internet, I doubt there's a market to support that many travel agents: the occasional honeymooners and niche travelers.

But the internet is great at turning niche ideas into massive businesses. If there are only thousands of people in your city who need this per year, you'd barely support a travel agency. But if there are thousands in your city, and also in every other city, that's a billion dollar business.