The deeper answer
What changes the decision.
Soffit closes the underside of the roof overhang. Fascia forms the vertical roof edge where gutters attach. Together they manage ventilation, protect rafter tails, support drainage components, and create the top termination for many siding details. Problems above the wall can send water down behind brand-new cladding.
Inspection should include stains, soft wood, peeling paint, loose aluminum wrap, pest entry, sagging gutters, failed end caps, and overflow marks. The estimator should also look at intake ventilation. Replacing solid soffit with vented panels only helps when the roof assembly has a designed path for air to move toward the ridge or other exhaust.
When replacement is needed, doing it with the siding avoids duplicated staging, demolition, trim work, and cleanup. Aluminum or vinyl soffit, wrapped or PVC fascia, 5-inch or 6-inch K-style gutters, downspouts, and splash blocks can be written into one coordinated scope.
If the components are sound, leave them. A serious estimate should not sell replacement merely because the crew is present. It should document condition, identify the source of any water, and separate required work from optional upgrades.