Not sure if you're looking for a legitimate answer or not but I can provide my take: to me, looking at that standard, I cannot make heads or tales of the pronunciation at a glance. Learning a whole new set of symbols and standards is simply more effort and less efficient in the long run when considering the amount of necessity actually required. I.E. it is not an incredibly common everyday issue. It can also be meaningfully resolved with something more linguistically universal (the known and taught alphabet), so the time spent, the effort expended, does not pay dividends and ultimately the half measure typically works near equivocally.

I am aware of Ghoti (fish) and Ptoughneigh (Tony) but really, those a more fun experimental ways to twist pronunciations and examples given generally sick to things people would know and understand the way to pronounce, and if not, could also be easily fixed. Even so many would not even second guess because the importance is usually of such low value that it can be wrong until corrected, further diminishing the value of learning a more rare and nonstandard (for general communication) standard.

Different dialects do tend to have slights to the pronunciation but again, it just feels like such a non-issue.

That's simply my layman take as to why I wouldn't learn it. I can't speak for anyone else