Tangent: I first stumbled upon the Tau manifesto several years ago, and though it made sense to me, I couldn't tell whether anyone took it seriously. Still wondering.
I was a Math undergrad when I first read it and I think the main reaction I got from faculty was 'dismissal' and the main reaction I got from peers was 'indifference' and, in one case 'annoyance'.
I think it took root in the pop-math education space [0,1], but overall I think most of the Mathematical world has dismissed it as trivial at best and unnecessarily disruptive at worst.
It's a shame, because I feel that understanding why Tau makes equations and concepts easier for people to grasp and build intuitions around is key to understanding why people generally find maths difficult and frustrating, and can give some guidance on how to bring down that barrier/activation energy.
People are looking at a bigger delta of improvement than that, IMO, but that also means they only want big commits from big names. The Tau thing really is too trivial, which means it may be outweighed by friction alone.
Yeah, the circle constant is considered 'solved' and has been a well understood concept since... (googles) .. oh wow, 2560 BCE [0], with pi being used as the symbol for the last 400 odd years [1]. It's understandable that there wouldn't be much appetite to tamper with that if there isn't a gosh darned good reason.
(Interesting to note the original coining of Pi was π/δ for what we now call Pi (circumference over diameter) and π/ρ for what we are calling Tau (circumference over radius).)
I think there's more basic opportunity for intuition and learning than pi/tau, which is using turns for angles. We tend to use degrees, which is less direct and requires memorisation/familiarity with magic numbers like 30, 45, 60, 90, 180, 720, etc. It takes more work to translate these numbers back and forth into angles (e.g. clock hands or pie charts) compared to twelfth, eighth, sixth, fourth, half, one, two, etc. turns. I think degrees should be left as a historical curiosity, like gradians, rather than the default we reach for in everyday life, from a young age (I can also see them being a nice 'mental maths shortcut', for those who are into such things).
I know many people struggle with fractions, which degrees can avoid (at least, on a surface level), but I don't know whether the highly composite nature of 360 would help, and fractions hinder, outside of classroom-style exercises. For example, 90 + 45 = 135 is easier to calculate than 1/4 + 1/8 = 3/8, but the latter might still be more intuitive as an angle (e.g. if answering with a diagram, or by turning one's body); and for anything more complicated than that I'd still reach for a calculator, even with degrees.
When problems require more sophistication than turns, we can introduce radians like we currently do. At that point tau makes sense as their conversion factor in equations, but it's still an unnecessary complexity when expressing angles; since any nice multiple of tau (or pi) can be divided through to get an even nicer number of turns.
It's in practice impossible to change a mathematical convention so deeply embedded as π. So even though a lot of mathematicians 'take it seriously' in the sense of agreeing that τ is the more fundamental concept, none 'take it seriously' in the sense of actually using it in public mathematics.
Tangent: I first stumbled upon the Tau manifesto several years ago, and though it made sense to me, I couldn't tell whether anyone took it seriously. Still wondering.