The reason for the aversion is that shotgun mikes have relatively poor sound quality off axis--uneven response, sometimes extremely uneven, with peaks and dips of 10 dB or so depending on the angle. Shotgun mikes are meant to help distinguish DIRECTLY on-axis sound sources from qualitatively different, environmental sound--not from reflections of the original sound. If you're recording indoors from any distance, the same sound reaches the mikes from all angles at once, and much of the desired sound will arrive off-axis. When it mixes with the on-axis sound, it degrades the quality of the pickup.
The other problem (for stereo recording) is that shotgun mikes have a narrower pickup pattern at high-mid and high frequencies than in the rest of the range. So if you arrange a pair of them in any of the common coincident or closely spaced arrangements, any angle and distance good for the low and mid frequencies can't possibly be optimal for the high frequencies, or vice versa. All the Williams formulas and curves, etc., are based on the assumption of polar patterns that are basically constant across the frequency range. Shotguns fail that requirement by a long, long way--the longer ones being worst of all.
As a result, professionals don't generally use shotgun microphones for stereo recording except for M/S stereo, where a well-placed shotgun can be a good center ("M") mike. Some very nice stereo mikes have been built with a shotgun as the "M" element, or a small figure-8 mike can be mounted directly above the capsule diaphragm of a mono shotgun. But that approach requires the majority of sound pickup to be direct/on axis. And the audience area of a concert venue is generally too far from the sound sources for that to be possible.