Why do programmers still use mailing lists? [duplicate]

Question

This question already has an answer here:

• Why do some big projects, like Git and Debian, only use a mailing list and not an issue tracker? 5 answers

Why do many open source projects collaborate primarily through mailing lists rather than through, say, forums? I may be ignorant in my assessment, but I, along with my communication teacher, think mailing lists are rather inefficient:

• It's hard to reference old messages. You have to wait until an archiving site picks up the message you want to link to, then look it up.
• It's hard to reply to messages you haven't received from subscription, since you have to manually copy the sender and message contents.
• It's impossible to moderate threads of discussion. Posts cannot be deleted or modified without supernatural powers.
• It's tricky to keep threads together (namely, to ensure all participants in the conversation are copied/replied to).
• It's tricky for users to participate in multiple high-volume mailing lists, as they have to subscribe and set up filters (or just be really involved).

What real edge do mailing lists have that didn't occur to me?