The thing about RPN is that it worked well as a sort-of "spoken not written" language. It's a clear and usable way to give instructions one-at-a-time to a calculator with a 1-line display.
But written out on paper, it's very hard to see what's going on at a glance, which is why nobody does this on paper.
Almost anyone programming in mathematical expressions of reasonable complexity today will spend much more time reading (and triple-checking!) these expressions than typing them. That's a strong reason to like infix notation, and in general notation close to what you would use on paper.
Those TI calculators are real cool, I cut my teeth as a programmer on a TI-83+ learning z80 assembly, but the truth is they're considered by many to be devices for teenagers. HP calculators seem far more popular in industry.
Of course, though, the marketshare of TI's infix calculators is much higher than HP's RPN calculators, and I haven't heard of much recent developments regarding HP's calculator line (the last I heard was HP had a limited-edition re-release of the famous HP 15c model sometime back in 2011, and also earlier this decade HP released a graphing calculator with a color display). But nevertheless there are people who prefer RPN to infix.