RGB and CMYK are like recipes. With each value an ingredient to make a colour.

Just like in the food world, the problem with recipes is that if two different people source their ingredients (a metaphor for ink and screen pixels) from different places, they may be trying to make the same food but the end result will probably taste slightly different.. sometimes it can taste completely different.

Pantone isn't really like a recipe. It's more of a definition. In our metaphor, it's like ordering your favourite brands version of the food, its made in the same way, in very controlled conditions and is likely to taste and look the same every time you use it.

Pantone colours within Adobe software are referred to as "spot colours" and when you save these properly into a print file (like pdf), they tell the printer to use specifically loaded inks into a printer.

An approximate value can be used, but because the printer instruction is lost without the license it makes sense to completely ruin what the image looks like, as if you just save this and sent it to the printer, they would use a CYMK value instead.. and this is usually never preferred if you are using spot colours in the first place.

TL;DR RGB and CMYK are ingredients, pantone is a definition. You can't always get to the result by using similar ingredients.. to be safe and consistent removing the colour is better than changing it, as it's more obvious something has changed from when you last printed that document.

(Edited for clarity and formatting)