Well, when we have an ambiguous and confusing way of expressing numbers and an unambiguous and familiar way of writing them, why should anybody ever use the former anymore?
The world is what it is.
The world could be better.
The world still is what it is.
Your software not handling Roman numerals won't stop people from using them.
There are times when making a futile stand against It, which will neither stop It nor slow It down, is necessary for your own psychological well-being. If you draw that line at the existence of Roman numerals, well, go in peace. However, saying that Roman numerals are pointless and shouldn't exist and therefore your software won't support them is really only screwing over the people who rely on that software because you insist on trying to derive Is from Ought.
People stopped using the þ and ȝ in English because the technology at the time couldn't handle it. People adopting new practices and habits to make it easier for technology is as old as technology.
There are few people who can read MCMXCVI fluently. It's not accessible for the majority of the population, with or without screen reader. Just don't use Roman numerals if you want your number to be widely understood.
Yes, but it will make my software easier to write, grok and maintain, all things that are beneficial to handling the 99.999% of the problem space that doesn't include an ancient way of writing numbers.
There's always going to be a painful tail of slow adapters with standards.