A car running well looks identical to one that's about to cost you a fortune. Worn brakes, slipping clutches, gummed-up fuel filters and tired oil don't announce themselves until they fail - usually somewhere inconvenient. Servicing is what catches all of that early, while the fix is cheap.
The other reason is resale. A vehicle with a full service history sells for noticeably more than one without. The stamps in the book do real work when it's time to move the car on, and they only happen if you actually have it serviced.
We're an independent garage, not a dealership, so the hourly labour rate is sensible and the parts mark-up is modest. The work is the same - same OEM-grade parts, same qualified mechanics - just without the overhead of a main-dealer showroom.
Most of our customers are repeat customers, year after year. That's the only signal we trust about whether we're getting this right.