Very good question. I agree 100% with the comments of Becky Katz and Sherry Hewins. I used to go to read the profiles of my followers and one or two of their hubs that interest me according to the titles. I would then decide to follow them based on those two aspects.
I have had people follow me without reading or commenting on any of my hubs. I have also had people follow me that read one of my hubs and commented on it.
Right now, I have close to 70 follows that do not read my work, or comment on my hubs or offer me encouragement or support in any way shape form or fashion. (If I didn't know any better, I would think they were following me for the sake of wanting to be on my feed...)
With all of the above being said, I no longer follow anyone.
I don't find it to be rude or crude not doing so.