US Visa Drop-box? advantage and disadvantages - Visa Waiver Program?

[tinkerbell]

Hi
Please may i know advantage and disadvantages of drop box.
FYI I recently noticed below.

If you enter the United States under the Visa Waiver Program, you are not permitted to extend your stay in the United States beyond the initial admission period. You must depart the United States on or before the date on your admission stamp when you entered the United States. See Extend Your Stay on the U.S. Citizenship and Immigration Services (USCIS) website.

[Kumar]

Dropbox is not an option, it is must. If you are eligible, system will automatically flag you to do dropbox. This changed with the New appointment System of Dropbox from last year

They are talking about different set of users from countries that are eligible for Visa free travel (see below), only for tourism. This does not apply for normal dropbox stamping that are done for visa renewal.