The hoarding has to be up before the crane arrives, the statutory boards have to be right before the first inspection, and the marketing suite has to look finished before the first viewing. Nobody has time for a supplier who quotes in four days and produces in three weeks.
What contractors and developers tend to need from one supplier: a hoarding scheme that survives twelve months outdoors, safety signage that satisfies CDM and the principal contractor, wayfinding for site traffic and deliveries, and a sales environment that looks like the finished scheme rather than the building site around it.