Yes, very good point! We talked in the past about people with bandwidth limits and total data limits and such. While tedious, with such an option in Core, they could set it to a speed that only downloads 5GB a day or so, to complete IBD in a bit over 2 months if that's the maximum their data plan or bandwidth allows them.
I know the vast majority of people wouldn't find it useful, and that's probably the reason it hasn't already been implemented, however as time goes on if we're going to expect more adoption, it could very well aid that. I know there are already alternatives such as a lightweight client or just not running a node, and don't get me wrong again the vast majority aren't going to be interested. I don't know, I just feel it could be worth it regardless, as it might just encourage someone who was already on the fence, to give running a full node a try, which obviously directly benefits the network as a whole.