I forget if this has been mentioned - but for bulking diets, it is primarily , IMO, to fit in the cals.
If your goal is 5000cals there is no way in hell youre gonna chow it all down in 3 meals.
I am currently after fat loss and plan on adding more muscle when I lose about 40 lbs of fat. I'm quite muscular already from years of training before my 8 year lay-off from training.
I do cardio on an empty stomach in the morning and by the time I finish in the gym, get a shower and get back home it is usually about 1pm.
So fitting in 6 meals between 1pm and midnight would be a lot harder than my current 4 meals.
I've only just switched to 4 meals so after doing that for a week or so I might try 6 meals and see how that goes.