Since I started uploading more frequently to YouTube I have come across more people asking for sub4sub. The main problem with sub4sub is that, yes it gets you tons of subs, but you don't get actual views and watch time. You also end up with a bunch of subscriptions that you will probably never watch yourself.
When it comes to getting people to subscribe to your channel you should want them to subscribe because you offer some kind of value to them. That value can come in the form of entertainment, education, or whatever else you might offer. That's why you should be doing a call-to-action at the end of your videos inviting viewers to subscribe, like, and/or comment. Doing that kind of reminds people that they can do all those things on YouTube.
It may seem to take a lot longer to grow a channel without sub4sub but if you don't take part in that sub4sub culture. You will be able to find your niche on YouTube that will allow you to grow your channel. That just simply doesn't happen with sub4sub because it just gets a bunch of people subscribed that will probably only last at most a month.
More recently I posted a link to my channel in a blogs comment section which got about 8 subs from. The problem was people commented saying "subbed, now sub back". Well as you can imagine once I didn't sub back all 8 unsubbed. That shows that they weren't actually interested in my content they just wanted to inflate their own sub count.
All-in-all sub4sub is a pretty terrible way to grow a channel and I'll leave you with a video on the topic. That being said if you want to watch my content and subscribe to me because of that you can find my channel here. https://youtube.com/thebensanders/.
Thanks for reading, have a great day! :)