I have a question so I'm a college student and when I go to school i take a book bag (obviously lol…

I have a question so I'm a college student and when I go to school i take a book bag (obviously lol ) on my back it's kinda heavy but not terrible I'm not complaining. I have like 4 textbooks and my laptop with my note books and pens and pencils I walk around campus well the other day my MIL offer more like insist to take my book bag so I let her and she complained it was too heavy for me and now she is pushing her son (my husband) to buy me a rolling book bag I don't think it's necessary I bet some of you have kids and pick them up it's just a book bag idk why she so upset ? can someone fill me in p.s my mom knows I carry that book bag and never says anything