Reading the article, the main use for the TLD check is to see if you have a typo, and if so suggest a correction - rather than automatically correcting the typo for you. Which I agree could be useful for the big email providers. (e.g you type gmial and it suggests a correction of gmail).

Also sometimes you don't even need the TLD:

user@myhostname, is a valid email address, and yet it's rejected by a lot of libraries.

Perhaps I do operate it. Can be very useful on say a dev box.

Perhaps users are aware of relative domain names and addressing. You even see this on a service like gmail's login. A user with the address example@gmail.com doesn't have to enter '@gmail.com' when logging in - just 'example'. But actually either will do. Further it's not totally clear for a user what to enter here. Is a username/id is the same thing as an email address or not.

My aunt swears blind that an email address without the name in double quotes and the domainy bit is not a correct email address. She types the lot out.