Why do EOS accounts have to be 12 characters?

Question

Why was the 12 character limit chosen for account names? Why can't I make a 4 letter account name?

Where can one see all the account names being squatted?

Answer 1

Why was the 12 character limit chosen for account names? Why can't I make a 4 letter account name?

As explained by Dan here:

Currently EOSIO prohibits the creation of new account names that are less than 12 characters long and/or contain a ".". The purpose of this restriction is to discourage name squatting.

Note, however, that name bidding changes the rules a bit as explained in the link above in Dan's proposal:

[I]t is desirable to enable shorter names for usability and because they are a marketable commodity.

It is also desirable for organizations to have the ability to create a "trusted" namespace where everyone can trust an account suffix like ".edu" or ".com". Shorter suffix enable longer names pre-suffix and therefore have a larger namespace and are more valuable.

The most economically efficient and fair method to allocate shorter names and/or namespaces is to sell the names at market price. To get the most value for the premium names they should not be sold all at once, but over time.

Answer 2

According to this, the 12 char limit is chosed to have better performances (i don't know how, for instance, using a 24 char name can inpact on performances...). To check the accounts already created you can refer to this answer.

Answer 3

You can view the short names auction here: https://eosflare.io/bidname