[luiscleto]

Yes, it's a good thing for sites and apps to be accessible.

No, it's not an obligation of any kind (nor should it be).

For companies that have grown enough to be providing services to (and profiting off of) a large enough part of the population, it would make sense to expect them to put resources into this. For someone working for free, trying to get an idea off the ground, or servicing a very niche subset of the population (i.e. a very restricted market) this blanket statement makes no sense and the costs it would add to make it an obligation would likely only cause a decrease in quantity of what is available (which, if deemed valuable, can be made more accessible later on) rather than an increase in quality of what's available.