You are using the notion of rationality wrong. Rational reasoning can only help you find how to achieve goals that align with your values. It is strictly worthless in choosing your values.
If a corporation has determined that profit maximization is their core tenet, excluding the needs of a minority of users can likely be deduced in a rational manner from that tenet. That is precisely why values need to be forced onto corporate actors through regulation, e.g. in this case through mandatory accessibility guidelines like EU directive 2019/882 that enters into force this very week.
Rational reasoning also takes into account long-term and second and higher order effects which quarterly profit-driven reasoning often ignores. If you support 95% of users and your competitor supports 100% then that may help your competitor getting 100% of them while you get none.
If a corporation has determined that profit maximization is their core tenet, excluding the needs of a minority of users can likely be deduced in a rational manner from that tenet. That is precisely why values need to be forced onto corporate actors through regulation, e.g. in this case through mandatory accessibility guidelines like EU directive 2019/882 that enters into force this very week.