Who said that milk and bread are unnecessary convience items? The drive-thru to get these staples is what's unnecessary.
For the record, I agree with most of what you said right here. That's why most stores around here encourage you to use reusable bags by offering a discount and why some people choose to not own cellphones and why many actually cook meals, not microwave them. There are times when all of these things are appropriate to use, but just not habitually. We should be able to live for weeks, if not months, without internet shopping, phone orders, ready made foods in their plastic containers, cell phones, microwaves, and plastic bags.
I have been accused of not seeing this argument from the other side. Whether or not you believe me, I do understand. That's why sometimes I find myself giving into ways of convience. I guess I would just hope that more people would be aware of the negative effects many of these convience items and services can have. If you choose to continue using them but are at least aware of what you're doing, great!