All stars rotate. And the more they contract the faster the rotation, so is there such a thing as a non-rotating black hole? And as gravity is less at the equator of a rotating star, assuming that they are still stars after collapsing to become black holes, at a very high rate of rotation could the escape velocity at the equator be less than $c$ while away from the equator it exceeds $c$? The fact that they still rotate and have a gravitational field after becoming black holes suggests that they are still stars even though we can’t see them, and gravity should still be slightly less at the equator of the spherical event horizon.
Yes, the expectation is that all (astrophysical) black holes have at least some rotation. Strictly speaking the chance of one having exactly zero rotation is zero. However, the rotation can be so slow that the non-rotating solution is a good approximation.