there must be some load on them...what else could have caused the cracks on mine? think about it the shocks must impart some reversing load on the towers when driving.
There is zero static loading on the shock towers. There are the damping loads during driving from the shocks but realistically you could drive 200k on potholed roads & they should survive unscathed. Not knowing the history of your car I can't comment. Is the car a rust bucket? Northern cars in the rust belt could have all manor of failures. Torsion bar mounts, spring mounts & frame rust outs sent most early A's around here to the boneyards in 1970's. That being PA, a salt zone where they have state inspections. Note the shock towers are virtually unprotected & will suffer max abuse from the weather and corrosion.