Evenings and weekends are often when the uninterrupted work actually gets done, and a fair few clients are at their desks then too. The awkward part is just the timestamp. An email that arrives at one in the morning can leave someone feeling they ought to reply at one in the morning, and a Sunday chase can land when a client was hoping not to think about work at all.
Scheduling settles that without changing how you work. Clear the backlog whenever it suits you, and let it all arrive on Monday morning.

