I have a small Youtube channel, well, two channels actually.
Both are small. Main channel has only 1.15k subscribers, sub channel has only 14 subscribers.
To answer the question from the OP (Scott), "the reason why you should (or shouldn't) subscribe", here's what I think, from "Youtube contents creator's" POV.
BUT, disclaimer first. I'm an oddball. A black sheep.
I have NEVER, NOT EVEN ONCE, asked to click like, subscribe, to support the channel.
I do everything that Youtube contents creators shouldn't do if you want to grow the channel, such as NOT niche down the subjects (My video subjects jumps around), talking firearms related subject and showing prop guns (youtube algorithm HATE that).
1) If there's a small Youtube channel you watch regularly, and you feel like you want to support that channel, then, subscribing to that channel, click like, leaving comment,
AND most importantly, watch the video all the way to the end.
2) If there's a big Youtube channel you watch regularly, with millions of subscribers already, whether you subscribe or not, it doesn't make any difference to the channel.
3)Here's an example of the latest video on my main channel.
As of typing this (7AM, Friday morning, video uploaded roughly 8 hours ago)
View count :118 (typical)
Subscription feed : 17 (14.4%)
Notification. : 9 ( 7.6%)
Youtube
recommendation : 83 (70.3%)
Subscribers. : -1 (One person unsubscribed)
Impression
click-through rate : 7.0%
Average view duration : 4.36 min (out of 11 min. video)
So, you can clearly tell, most of subscribers actually don't watch the videos.
Out of 1,000 subscribers of my channel, only 20 or so people actually follow / watch my videos.
The video itself