Wheel studs coming loose

Three times when I had my car in for routine service, including tire rotation, the mechanic found 1 or 2 wheel studs bad and had to replace them. Two different shops. What is going on? Bad design, bad mechanics? should I just get 4 steel wheels when I need to replace the tires (but that is not for another 30-40k miles)

2015 Subaru Forester, alloy wheels, 40k miles.

Wheel studs appear to be of standard design. What was wrong with the bad wheel studs? By any chance did he show you the bad studs?
The only thing I could think of is the person doing the tire rotation cross threaded the lugnuts.
I see no benefit in changing to steel rims.

I’m thinking that somebody has been applying a little too much torque to the lug nuts (or leaving them all loose).

I wouldn’t blame stud or wheel design, but would look to human error during rotations.

Many folks choose to do their own rotations and oil changes to prevent finding fasteners/plugs missing, loose, or over-tightened.

Human error was my guess also. But one mechanic was the dealer, another was a trusted mechanic.

The Toyota dealership I bought my car from torques the lugs to at least 3 times the spec even after I complained and the service writer says it can’t be happening because they use a torque stick. Another Toyota dealer torques them right to spec as does my tire dealer.

I would rather rotate my own, But to maintain the tire warranty I need to have proof of 6000 mile rotations.

Perhaps the trusted mechanic had only received the problem that was created by the other shop (or the other way around). The studs could have had damaged/weakened/stretched threads as a result of previous improper handling.

Wheel studs become loose when the lug nuts are over-torqued.

Over-torquing the lug nuts causes the wheels studs to stretch. This then causes the stud’s splines to become narrower where they no longer grip splined holes in the hub flange.