One possible explanation: leaded solder is more elastic than non-leaded. (less brittle)
Modern mass produced products generally have had lead engineered out of them, including in the solder.
One popular product specification in this domain is RoHS, the EU Restriction of Hazardous Substances Direction, which largely bans lead and 9 other hazardous substances:
Although note that avionics fall under the "transportation" exemption, and RoHS does not apply.
That said, the supply chain has moved largely towards RoHS compliance, so some avionics inherit that for supply chain simplicity. Some don't; there's a cottage industry reballing BGAs from lead-free to leaded solder for aerospace applications.
Modern mass produced products generally have had lead engineered out of them, including in the solder.
One popular product specification in this domain is RoHS, the EU Restriction of Hazardous Substances Direction, which largely bans lead and 9 other hazardous substances:
https://en.wikipedia.org/wiki/Restriction_of_Hazardous_Subst...