Unfortunately, the life of a 'gigging' musician tends to encourage this end result.

The following is MY experience only & when I say musicians I am talking about pro's & semi-pro's in folk, country, blues & rock. Lots of work in working mens clubs in the North of England.

All my musician friends/acquaintances are either divorced, separated and/or big drinkers. (I can actually think of no exception to this but hope there is one).

When you turn up for a gig you need to be there before the audience so you arrive early to set gear up, sound check etc.
The landlord/host offers you a drink.
When set up the audience start to trickle in & some fan will insist on buying you a drink.
In the break, old & new fans will offer drinks as will the host.
Members of the opposite sex will become 'friendly'. If you have been on the road for a while this can be very tempting.
When the gig is over you have the gear to clear away. Often the landlord/host will offer a drink whilst you do so.

For a solo performer it is a lonely life & the temptations are great.
Amazes me that there are lots who don't become alcoholics.

Still annoys me when a 'professional' act cannot deliver the goods though.