Two questions.
1) if I skip ads on a video via Smart Tube Next, does this directly reduce the creator's income? 2) why do creators ask for likes and subscribe, does this directly increase income?
replies(1):
1) probably not directly. Eventually the advertisers might notice a decrease in effectiveness lower their investment in that area (either by lowering the amount they are willing to give the creator for a sponsored segment or not doing sponsored content entirely). Eventually if they think the ROI isn't there they will reduce their spend.
2) You have to feed the algorithm beast to be successful. Even channels with high subscriptions still get a tremendous amount of views from YouTube's recommended algorithm. One big part of that algorithm is "Engagement" which includes the number of subscribers, likes, and any other engagement on the video (such as comments, which is why you'll see a lot of comment-bait questions in videos now like (if you disagree let me know in the comments).