The key concept is learning from the mistakes of others, instead of repeating them. The past several decades provide numerous examples of people picking "internal" top-level domain names that they were 100% positive no-one else would ever use … until someone else did, sometimes as a result of the exact same thinking.

* https://jdebp.uk/FGA/dns-use-domain-names-that-you-own.html

* https://news.ycombinator.com/item?id=45144631

You can find the case of dev. in particular discussed in umpteen places here on Hacker News over the years.