We do have an equal temperament scale! That’s what most music uses. What we don’t have is just intonation which uses simple ratios/intervals for the notes. It’s just intonation without the beating, equal temperament, which was listen to all day has the beating but we’re adjusted to it.
Do we? My impression was that strings, woodwinds, choirs instinctively tend to use just intonation, and Wikipedia entries for both just intonation [1] and equal temperament [2] seem to back that up. That's why symphony orchestra players will often have a different flute, clarinet, or oboe for different tunings. It's just fretted instruments like guitars that are by nature equal-tempered.
On a side note, both Wikipedia entries reinforce my original point that the mathematics of this is fascinating.
[1] https://en.wikipedia.org/wiki/Just_intonation
[2] https://en.wikipedia.org/wiki/Equal_temperament