Many people are apprehensive about being linked to their plates, even going as far as blacking them out in selfies etc. Given this apprehension (founded or unfounded), I doubt the increase in business would be worth the trade off in negative PR. I can't begin to imagine what the Wendy's twitter timeline would look like if the news broke that McD was storing your license plate in a database and correlating it with your income.
Many of the ideas you suggested (recalling past orders, upselling) can easily be accomplished with existing smartphone technology. I've never used the McD app so I don't know if they utilize location tracking but if they do I can almost guarantee they are already checking to see which locations you visit the most, what you order, when you usually come in, whether you use the drive thru or not, etc. Even without location tracking they can still do all of that if you order online.
tl;dr In my opinion they don't do this because they can already collect the data through less invasive means.
Many of the ideas you suggested (recalling past orders, upselling) can easily be accomplished with existing smartphone technology. I've never used the McD app so I don't know if they utilize location tracking but if they do I can almost guarantee they are already checking to see which locations you visit the most, what you order, when you usually come in, whether you use the drive thru or not, etc. Even without location tracking they can still do all of that if you order online.
tl;dr In my opinion they don't do this because they can already collect the data through less invasive means.