Deserve to bike and "deserve to force bicycle manufacturers to make mass-produced models that super serve the super-sized even though they're a significant minority of the actual and probable global customer base" are very different things.

If you want a bike for someone 300+, get a used, big steel frame and start assembling. Same for weight weenies the want bikes as light as a feather: customization is on you. Mainstream, pre-assembled bikes are going to be made for the majority of people that are likely to buy them, because otherwise they won't sell.

Again, to emphasize: AT EITHER END--super comp or super weight--bikes are specialized (not the company) bicycles that require parts selection and piece-by-piece assembly. It's not "unfair" to morbidly obese people anymore than it is unfair to someone that wants a super light bike or a super durable, weight-bearing, bike-packing ride.

My friend is 6'5 and all muscle, idk how much he weighs but it's got to be a lot. He had to build a bike from scratch as well. He would pop spokes and mess up frames. It's not about fat it's about weight. Less than 2% of the population in the United States weighs more than 300 pounds, and I imagine only a fraction of that fractional subset of people intend to ride a bicycle.

Also, "custom" does not necessarily mean expensive. It just means building it up piece by piece. Many people who have very little money but want a decent bike also build "custom" bikes from used parts, because you can slap together a decent bike from good used parts rather than spend the same amount on a Walmart special that breaks apart in two months.