I would argue too that you have a "wear layer" on 3/4" hardwood too. Why? Because after about 5 to 7 mil you will start to run into the tongue and groove of that floor. You cannot endlessly sand the 3/4" solid floor or you will end up getting into the tongue and groove portion of the 3/4" hardwood. Yes, that would take an awful lot of sanding, but my point is it is not endless. Also, may I add that most customers when asked how many times they hired a professional to come in and re-sand and finish their 3/4" hardwood floor, 99% of them say they never have. Most people don't want to go through the process of paying to re-sand and re-finish their hardwood. It's not cheap.... This is also why engineered hardwood is a great option. Many engineered hardwood options give you a factory 25 to 50 year finish warranty with stains and finishes that most of the time cannot be duplicated in the field. Lately, I have seen some engineered hardwood selections with stains and finishes that are simply amazing. When it comes to installation, most of the time installation is exactly the same way for both products... except with engineered hardwood the customer doesn't have the extensive labor cost of sanding and finishing the wood in their home making it much more cost effective. Personally, I love them both, but would lean more towards the purchase of engineered hardwood for the desire of the manufacturer's custom stain colors, finish warranties, overall cost and structure stability.
Image of an engineered walnut