Yep, I think senior discounts are partly/largely about willingness to pay, not ability to pay. For example, senior citizens aren't the target demographic for most movies. Theaters get full freight from the 18-45 crowd, who want to see the movies the most. Then they entice senior citizens to come watch movies that they don't love by giving them better pricing.

Same applies for theme parks, where the target audience is young adults and families with small kids.

I'm not defending any of this — just pointing out that price discrimination is sometimes about ATP, and sometimes about WTP.