If somebody is following you, every time you publish a new article they will be alerted - so they might comment, or share it on their facebook/twitter. While this is unlikely for many to generate much, if you've got 1000 followers then at least you've a chance that when you write something new 1000 people will be notified... whereas if nobody follows you then maybe nobody will notice/care.
Your hubs don't show the top slot Adsense advert until your page has had 100 views, so it's a way to potentially generate those 100 from hubpages people (who won't click the ads anyway in most instances).
If you follow people, you get notified when they post - and can comment on their artice.
Overall, the monetary potential of this is "medium", the reality is more likely to be "none". But, it does help to get you noticed and if you go into the forums you've got people there who know who you are possibly.
It's all a bit airy fairy to be honest, unless you've super-proactive with commenting etc.