New to all this?
Start with the whole approach behind Parent Play Style.
See Parent Play StyleYes, it's usually fine to let a child stay in goal every single game.
When a child only wants to play goalkeeper, it isn't a sign they're avoiding football, it's usually because goalkeeper is the one position whose job never depends on anyone else's pass or positioning. That clarity, not a dislike of running around, is almost always the real appeal.
I spent a good six months privately worrying that always being in goal meant he was avoiding the actual game, before I noticed he was the one begging to play at all, every single evening, as long as he got to be keeper.

The plain mechanical reason
Every outfield position comes loaded with a small dose of uncertainty: where to stand, whether a pass is coming your way, whether a mistake is about to be visible to everyone else on the pitch. Goalkeeper has one unambiguous job instead, stop the ball in front of you, and that job never depends on a teammate's decision or timing.
For a child who likes knowing exactly what they're meant to do, that clarity is the whole appeal, not a dislike of running around. A child obsessed with playing goalkeeper has usually worked out, without ever putting it into words, that the position removes the guesswork the rest of the game is full of. The ball arrives, or it doesn't, and either way the job stays exactly as clear the next time.
Preference or something to watch
A kid who always wants to be in goal is not, on its own, something to fix. Two things are worth telling apart.
A real preference is fine to let run. A child who happily plays goal every single time, and is clearly enjoying every minute of it, doesn't need managing out of that choice.
Avoidance is worth a gentle look. If outfield time specifically brings out reluctance, or visible worry about getting it wrong in front of others, that's closer to a fear of getting something wrong than a simple position preference. In that case, these games for a child who's nervous about the ball are worth trying alongside this one.
One idea, borrowed carefully
The American Academy of Pediatrics encourages families to let children try a range of sports rather than narrowing in early. As the AAP's own guidance on sport variety puts it, "if we offer children a variety... they are more likely to try new activities and stick with the ones they enjoy." That guidance is about trying different sports, not different positions within one sport, so it's borrowed here as a related idea rather than applied as if it were written about goalkeeping specifically. The same underlying logic still holds: breadth protects enjoyment, and pushing a change too hard risks souring the very thing you're pushing a child toward.
A low-pressure way in
The easiest way to introduce outfield time is to give it its own clear job, not frame it as leaving goal behind. "You're the only one allowed to score tonight" works far better than "your turn to stop being goalkeeper," matching how we handle two children sharing one game with a real job for each of them rather than a watered-down version. The swap works because it replaces one clear job with another clear job, not clarity with uncertainty.

Quick answers
Usually yes. A genuine preference for the one position with a clear, unambiguous job is common and not something to correct on its own.
At this age, garden play is about enjoyment, not development pathways. If outfield time is offered occasionally as its own clear job, that's enough.
Give outfield time its own clear job, like "you're the only one allowed to score tonight," rather than framing it as leaving goal behind.
Keep going
Three places to go next, depending on what's going on for your goalkeeper. If your child would rather not defend at all, what to do when a child hates defending in football makes it worth their while. If they want to stay in goal, goalkeeper gloves for kids, and what size says whether they need them. And if you wonder which position suits a child, what football position suits your child looks at all of them.
Start with the whole approach behind Parent Play Style.
See Parent Play StyleIf outfield play brings out real worry, start here instead.
See the nerves-first approachThe actual hands and footwork behind a clean save.
See the catching guideTonight's five minutes
One clear job beats a demotion from the job he already loves.