I do packing slips! My websites are responsive for phones etc but i am not going AMP, i would rather take a hit on google ranking. When i update a blog i use a SEO program, i tend to get low scores, i do this on purpose so my copy dosnt resemble others.
I avoid keyword saturation and all the other things you are supposed to do. But I do have another site that is google friendly and google indexes it well, i use that site to link into my others. I also have a copy that is Bing friendly, but oddly the sites are not IE friendly, IE is dead as a dodo i have no idea why people use it!
IE is not HTML5 compliment despite MS saying it is, it has trouble with CSS3, but so does firefox which is why CSS3 has all the mozilla crap you can put in.
Packing slips, statements and invoices are essential the way i see it. But our business tends to be run the old fashioned way with modern touches to make things easier for people. I have adds on site, but they are my adds and are there to make things easier for people. the adds are not intrusive and on the whole make the shopping experience easier. if your on a section thats for information or the forum then there is no adds.