Because there is far superior antennas cheaper, like a Sirio tornado 27 for a start, they are also notorious for tvi/rfi and static, they are not isolated from mast,not provided with radials,they are notorious for going threadbare, it has very lossy coil system,they are nowhere near as windproof as people make out, they will work dx in good conditions,so will a coathanger, see how good they work at solar minimum, they are poorly constructed and soldered by welders or blow torches,
and as for using them multi band, hmm, they are pretty lousy on the band they are designed for, god only knows how inefficient they are elsewhere, but hey, don't let me put you off them, as far as i'm concerned the more people using them the better, less competition for me,lol.
a dummy load has a good swr over a wide bandwidth too, but i wouldn't be mounting one on my mast, i've probably missed a few drawbacks,
i always hear the same argument for them, i worked here or there on it, big deal, i worked Australia on 18w out a sirio hp4000, but i certainly wouldn't be putting it on my roof,mast or tower, it was just down to good conditions, judge an antenna in bad propagation times not good times.
you could take a piece of coax cable, turn it into a T2LT and it will outperform an a99, mounted on a fibreglass mast or hung from a tree it will whup its ass, time after time. a T2LT is coaxial 1/2 wave version of the Sirio gainmaster, the way the Bigstick should have been made, and it doesn't need radials to be efficient as its a centre fed dipole that is both isolated and choked, nor does it need impedance matching. it also has a far superior radiation angle for dx.
not sure it will be as multiband though as i don't believe in ATU's,
I can only assume the i in 9.9Dbi refers to idiot as a reference point, because only an idiot would believe any vertical non colinear antenna will have anywhere near that gain.Unless your target radiation angle is aimed at worms or clouds, and I ain't convinced there's many of them on CB or any other band.