The Surveyor 3 hardware had spent several years exposed in space. Until this point most 'samples' had spent at most a couple of weeks in orbit, with the exception of a sample collection plate recovered by Gemini 10 from the Gemini 8 Agena target vehicle after 6 months.
Space exposure is hard to simulate and, prior to the ISS making this much easier, several dedicated missions had flown just to expose materials and equipment at non-zero cost and risk.
Apollo 12 gave the first opportunity to see large amounts of material after several years exposure. In particular, the camera was of interest for robot missions, where having the camera work for years would be required, since this particular camera had failed for reasons that were unclear.
There was also scientific interest in the material that had accumulated over a known period in/on the surface. Collected lunar rocks provide information, but it can be unclear how long they had been bombarded, whereas the paint of the craft was of known age and composition, so changes could be quantified and used to quantify changes in the rock samples.
The full report of this is available. The summary includes the words:
These results indicate that the state of technology, even as it
existed some years ago, is capable of producing reliable hardware that
makes feasible long life lunar and planetary installations.
suggesting that, at the time, the most interest was in designing future space craft that needed to operate for years, and that this study proved that it was indeed possible.
The studies included 12 on the the parts with view of improving future craft, four on organic contamination and success or otherwise of sterilization measures (of interest for Mars missions), 7 on micro meteorites, 9 on long term radiation exposure and one on the surprising amount of damage done by the somewhat distant touchdown of Apollo 12, highly relevant to any future multi craft missions.
It is however probably relevant that none of the following missions landed near existing hardware, suggesting that the perceived value of doing so was lower.