Well, i've begun to do it when i realized several people contacting me this way had an exponential growth doing so, but i quickly stopped after a first few days, it was really tiring (it's just fucking mind crushing for me to get from people to people and with my health issues i don't know why i would tire after an hour doing it, my eyes would close and i had to resort to have a fan blowing cold air on my face to keep being awake, it's a very very tedious thing and it's like, draining energy from your soul x) or it might be that i was in a very low depressive state at that time because i have those kind of health / mental issues and it can happen that i sleep for 12 hours sometimes.) and a really, really huge waste of time when i could be drawing instead or make blog posts pertaining to things i am really interested into, interact on other social medias.
So i am guilty to have done it out of experiment, it's true that you get a whole lot more readers this way as you are not being shown on front pages or any other ways than updating your webcomic, wich i do maybe once or twice per month in bulk of a lot of pages. You could say i could just upload one page from time to time to get more exposure, but people like it when i give them at least 4 / 5 pages to read at a time, or more, it kills the growth taking this much time between updates, health and psychological / anxiety and maniaco - depression issues doesn't help much either.
I also think it's about "how" you contact people, when i've done it, i asked politely, it was a question, if i could invite them to try it out without forcing the manoeuver or seem harrassing, unpolite, you have to at least put the manners and the correctness while doing so. Some people don't even ask a question doing it, they almost urge or rush you to check it out, wich is not how you invite people to 'try' it to see if they like it.