Why do you allow concerts to clash with other local events?

We do try to avoid clashes with other local concerts, fireworks, major sporting events and anything else that might reduce our audience. However, our concert dates are heavily constrained by the availability of the hall, our conductor, our soloists and the need to rehearse during term time when most of our members are around. We have found that attempts to reschedule a concert often simply result in a different set of clashes.