When I first started guitar lessons, my teacher was VERY strict......'twice per week or don't bother'! After a while I was playing with group.......getting some gigs......radio etc. He told me ,"You'll have to make up your mind.....singer or guitarist? You can't be both!".
I switched teachers! Many years later I can understand his feelings........loss of practise time etc. Although these days there are some fine guitarist/singers....then it wasn't so common.
When I started singing with my wife.....we were covering different types of material. She was able to help me with the "straighter stuff"........I (hopefully!) could assist with phrasing..feel for the genre etc.
Then when our son started playing, I found that I had to practise harder just to keep up with him!
It was about that time that I heard a famous concert pianist remark that ...."He could spend hours practising a 4 or 8 bar passage".......I thought, 'If a musician of that stature feels the need to do that....surely I'm not doing enough!'
From then on......I've had PROPER practise sessions on both guitar & banjo every day......AND basic singing practise.....breathing , diaphram control etc. BIAB is a great help with all of these......and it's a great feeling......(I'm sure many musos here will recognise it!)......when you discover you can play a piece now....that you couldn't play before......or sing something similar!
I hope I'm not hi-jacking this thread.........some singers are WONDERFUL musicians......and some MUSICIANS are also GREAT singers! (My old guitar teacher may be turning in his grave!) Regards, Joe G.