As in you can only purchase tickets online? This has sadly become common practice, where at best ticket providers just require an email address (to email the digital ticket to), but at worst requiring: email address, full name, password (for account creation), date of birth, gender, full address, phone number, and aggressive bot detection scripts (presumably against ticket scalping); most of which used to market upcoming events, based on demographic.
The last one I attended still accepted payment at the door (which is rare enough), but refused to accept cash when I tried... But at least I limited information directly available to the ticket provider and venue; which is something.