Wouldn’t it be a lot easier if all of the Jedi just used the same lightsaber hilt model? In real life, many products that we use on a daily basis are mass-produced. A car is common example. Assuming your car is a somewhat common and relatively recent model, if something breaks or goes wrong with your car, a mechanic could fix it because they have likely seen a car like yours before and could find compatible replacement parts.
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If something goes wrong with a lightsaber within the Star Wars universe, every lightsaber is a little different. Lightsabers likely differ the most on the outside. Many of the internals are likely somewhat similar, but everything about a lightsaber is tailored to the user. Each Jedi likely modified or repairs their own lightsaber, when necessary.
Real life lightsabers (e.g. Ultrasabers, Vader’s Vault, Sabertrio, etc)
Lightsabers break in real life too, of course. Some lightsaber enthusiasts will fix their lightsabers themselves. Other lightsaber enthusiasts will send their broken lightsaber to a sabersmith. In real life, the lightsaber wielder can hire someone to fix the lightsaber for them, whereas in the Star Wars galaxy, each Jedi presumable knows how to fix their own lightsaber.
Imagine a Star Wars galaxy with mass-produced lightsabers
If the Star Wars galaxy used mass-produced lightsabers, more like blasters, fixing the lightsaber would be easier. If a Jedi’s lightsaber gets lost or broken beyond repair, the they could easily switch to a new one of the same style and they wouldn’t have to adjust to the look, feel and balance of a different weapon. Obi-Wan Kenobi and Anakin Skywalker both are given replacement lightsabers in Star Wars Episode II: Attack of the Clones. It must have been very strange for them acclimating to a different style hilt.
Benefits of unique lightsabers
It’s certainly a lot more exciting for Star Wars fans to see different characters use different lightsabers. A lightsaber is seen as an extension of the personality of the Jedi. The emitter, body and pommel of the lightsaber all reflect the personality of the builder. Even the blade color differs, although most Jedi lightsabers use a blue or green blade. If you asked 10 Star Wars fans which lightsaber is their favorite, you could easily get 10 different answers. Even the Skywalker lightsaber remains a common fan favorite, some people strongly dislike the hilt style, too.