Here is why I think these kinds of dynamic pricing practices are bad: it may be perfectly fair and legal, but it forces a non-negligible number of humanity to waste time and/or energy to figure out if it's happening, how to work around it if it is, and just generally waste human potential on something that should be a simple commodity.
Why is anyone forced to reverse engineer the pricing scheme? Simply decide if the ticket is worth the money to you. You typically have other airlines to compare to, other fares on the same airline for different itineraries, and other modes of transit entirely. Just because some people won’t buy anything that isn’t on a coupon doesn’t mean coupons are bad.
Which is bad for consumers and the broader economy.