But working together they can keep out those non-union 'Scabs' that could get the job done.
The nonunion crews who were turned away were not turned away by the customers. They were sent letters/emails by the IBEW fraudulently telling them that unless they unionized or contributed money to IBEW pensions, they were not legally allowed to come.
All this was done sneakily, because the unions knew that if they tried to get the public to protect their monopoly, the public would tell them to go procreate with themselves.
In Port Monmouth NJ today, Italian restaurants were offering free meals to power workers from right-to-work Georgia. I'm sure local IBEW members are quietly fuming about that, but they wouldn't dare open their mouths about that now.