Dexterity represents agility and acrobatics specifically is meant to represent balancing and tumbling. Athletics (Str) specifically is used for jumping. Dexterity is already too powerful and Strength is too weak in 5e - allowing characters to use Dex in place of Str for jumping just worsens that divide. People can jump far because of their muscles.
Taking into account character load would be more realistic, but it'd also unduly punish Str-based characters because they're more likely to be wearing heavy armor. I'd want it to be a fairly minor effect: an 18-Str character wearing heavy armor should still be able to jump farther than a 10-Str character wearing no armor.
