They won't/can't. Their only real options are to fallback to either the "text" field or the "numeric" field.
> Why reinvent the wheel? Why not fix whatever problem you have with numeric input?
JS devs will prioritize chasing after their ideal UIX long before they consider things like JS being disabled, screen readers, ARIA tags, cross-platform compatibility, etc.
There's countless replacements for long-supported HTML input fields that still get active development: date pickers, numeric inputs, sliders, you name it. If it exists in the base W3C spec someone has likely reinvented the wheel for every purpose from pixel-perfect skeuomorphism, to aggressive input masking, to "instant feedback," to vaguely claiming "you cannot trust the number input" - the list goes on and on.
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OP if you're reading this - I hope you're considering JS being disabled (graceful + functional fallbacks), ARIA, aggressive cross-platform testing, and testing with real screen readers. If you aren't, this is not an accessible service.