Guitarists tend to want their cab to be their main monitor - and that is why they are a complete pain in the backside. Wedges are far superior (as it kind of helps that they are pointed at player's ears for starters) as there is less bleed into the vocal mics (obviously the correct placement of wedges according to the pickup pattern of the mics is obviously a consideration). Again, depending whether you go for directional wedges, or wide dispersion wedges means that you should get a better mix across the stage, with less bleed into open mics.
Even better is IEMs, even better still is a silent stage. Springsteen has got his "big amp, big speakers set up" right. They point skywards and are miced from above. Mind you, he probably only plays stages where mic bleed is less of a problem... and is more about cranking the amps without killing the ear drums... with the wedges doing what they need to do.
If guitarists actually played for the band rather than for themselves, things would be a lot better - and that is making more use of wedges. Trouble is, in a lot of venues where house PA budget is always on a shoestring, it's always the monitors that are the first to be cheapened out - to the extent where they can't cope with what needs to be thrown at them. Dispersion of guitar cabs shouldn't really come into the equation at all...because if they can be heard over the PA and create problematic nodes in the room, the PA monitoring isn't being utilised properly.
Trouble is, you can't tell anybody this and everybody always knows best, despite not being able to beat the laws of physics. Guitarists in particular, are always stuck in the way of thinking - well, this is how it was done in the 60s...