As long as the toe is reasonably close, there are 4main things that will cause a “pull”.
1) low air pressure.
2) a shit tire(s), broken cords, separated plies, bad wear patterns, etc...
Usually but not always, the “pull” will be in the direction of the bad tire, but it can “push” to the opposite direction, rare but it can happen.
3) excessive difference in caster angle, like a degree or more. McPherson strut suspensions seem to be less sensitive to caster issues. When they do have a caster issue, it is usually because the control arm took a curb shot and the wheel is sitting back in the wheel well. Obvious damage. Ideally the right should be 1/4-1/2 degree more to compensate for the crown of the road.
4) some asshat put wide ugly black wheels on the vehicle and now the center of the tread is nowhere close to the steering axis inclination line.
Often times when i do an alignment and they say it has i pull, it doesn’t. The steering wheel is simply off center while driving straight.