Mail Lists Q

Huh, hadn't thought about mail lists in eons, I think; at least 
years.  They almost always seem to unleash almost a ddos attack 
on one's inbox and many unsuspecting newbies seem to still get 
caught in them, no matter how well the descrips warn people about 
the possible onslaught of messages.  Which brings me to my 
question/s:

What purpose and what kind of person would subscribe to a full 
blown mailing list?  What use could they be?

I've thought about databases; no, way too much crud to pick thru. 
A very lonely person?  Maybe; if they like to read.  To learn? 
Suppose that's a possibility.  A mailing list could help one cull 
out the misfits ahead of time I suppose, and there is a lot of 
good information hidden away in the many mails, but ... sheesh, a 
couple days/weeks of lurking will do the same thing, and probably 
a lot quicker.

Anyone got any responses that might make me feel like I have one 
less ignorance-area in my life?

Regards,

Pop