Aspheres are useful if weight and length are significantly more important than cost. For polychromatic objectives, they don't necessarily reduce lens count and they only improve performance if a design is already extremely weight or length constrained. Manufacturing cost is increased (more complex polishing), and assembly cost is increased (tighter tolerances on tilt / decenter).
From my viewpoint, aspheres are just another tool in the optical design toolbox. Like any other tool, it is very useful in some cases and not so useful in others. I would avoid their use for LF optics because (a) you're not operating at a lens speed where they can help size/weight, and (b) the production volumes means just the aspheric lens itself would cost as much as a good used pickup truck.
You see them in fast SLR lenses because they help size and weight, and are produced in numbers that justify the cost of the (prototype ~$10k / production ~$100k) mold.