Specific and/or direct examples? I can't immediately think of any, but it seems likely that, because human society is largely a matter of institutionalizing and perpetuating the socialization between heterosexual males and females, avoiding this consideration in the creation of social norms out of a desire to make an inherently small minority feel less alienated will take away more utility from the majority than is gained from the minority, resulting in a net utilitarian decline. As an example, changing the American currency, which presently causes difficulties for the blind (and yes, I know its not the exact same category as the three examples I gave), is likely to be highly inconvenient for people who rely on automated transactions much of the time, such as at grocery stores or vending machines, as well as current manufacturers of such equipment, not to mention the inconvenience of holding differently sized bills. If, however, there is am inexpensive way to change the design of currency without making them incompatible with current machines or unwieldy to use, then that would be a reasonable accommodation that should be instituted for a disadvantaged minority.
I agree, however, that one should always be aware that such assumptions are just arguably necessary shortcuts, and could always be wrong.
Edit: this is a reply to Silvanus, I forgot to quote him.
