I think custom domains are a tool for price segmentation* (like a student discount). Medium and Wordpress want offer a free product (for marketing/network effe

I think custom domains are a tool for price segmentation* (like a student discount). Medium and Wordpress want offer a free product (for marketing/network effects), but also have their higher-end users pay. They do that by limiting a few features their higher-end users need to the premium product to force them to buy. In this case, it's custom domain that lets you look more professional. You see this with email too. Want to use your own domain and look like a real business (vs. some dude with small-time aspirational business-hobby run off of gmail)? Then you pay $5 a month or spend your time being a sysadmin. * https://en.wikipedia.org/wiki/Price_discrimination https://en.wikipedia.org/wiki/Price_discrimination