Great idea. I'll suggest that and hopefully they will listen!
This is the type of feedback you should be providing to McDonald's via the corporate website. You should also leave feedback on the McDonald's app rating system so the app development team can see your comments. You aren't reaching the developers or corporate management leaving feedback here on Google.
Each McDonald's is independent. They may all have the national deals such as the 2 for 5 Bigmac but each location may have other specials that they run on their own. That's why you may not see all the deals online.
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