Players talk about string type constantly and about stringing quality rarely. The machine and the person operating it decide whether the tension a player asked for is the tension they get.
Tension is lost during the job
String is pulled to a reference tension and then clamped, and every clamp releases a little as the tension transfers.
By the time the last main is tied off, the first strings have already relaxed, so a racket never holds the number set on the machine.
Good stringers manage this with pull order, clamp technique and by working quickly, since string relaxes measurably while the job is in progress.
Constant pull versus lockout
Lockout machines pull to a tension and then stop, so the string relaxes against a fixed clamp and settles below the target.
Constant pull machines keep applying force while the string creeps, ending closer to the requested tension but effectively stringing tighter than a lockout at the same setting.
Neither is wrong. It means a number is only meaningful alongside the machine type, which is why players who change stringers change their numbers too.
Pattern and grommets shape the result
String pattern density changes how much the bed deforms, with open patterns allowing more string movement and more spin and closed patterns offering more control and durability.
Grommet condition affects tension directly. A worn grommet lets the string cut into the frame and creates friction that prevents even tensioning.
Skipped holes and shared holes in a frame's pattern also have to be strung as the manufacturer intended, or the frame is loaded unevenly.
Strings lose tension whether played or not
Polyester strings in particular relax quickly after installation, losing a noticeable portion of tension in the first day regardless of use.
Natural gut holds tension better and is far more sensitive to moisture, which is why it is treated carefully and rarely left in a hot car.
This decay is why professional rackets are strung on the day of a match rather than in advance, and why fresh frames are cycled in through a match.
Why players travel with a stringer
Consistency is the whole objective. A player who feels a difference between two rackets cannot tell whether the cause is the frame, the string or the job.
Using one stringer with one machine removes two of those variables, leaving only the frames, which can be matched.
The result is that stringing is treated as part of a player's equipment setup rather than as a service purchased wherever the tournament happens to be.

