Wobbling steering wheel when braking

2005 Chrysler Pacifica Touring
When pressing on the brakes at speeds over 25 the steering wheel wobbles. I have had this problem in the past and it has been diagnosed as warped discs. They have been turned and it fixes it for a while then it comes back and again warped discs. I have had the discs replaced but it has come back time after time.

Just had it checked out and they are saying it again, warped discs and this time cannot be turned need to be replaced but they also showed me I need new lower arms.

What do the lower arms do? And if I do not replace them will I have the same problem later with the front discs getting warped?

Any looseness in suspension components or wheel bearings can create a symptom that can be mistaken for warped discs.

Warped or problematic discs are also not necessarily a wild guess. That can be verified with a dial indictor and micrometer.

Lower control arms may or may not be a critical need.
Worn bushings lead to irregular tire wear, wander, or brake shudders; all depending upon the severity of the wear.
A worn ball joint (which is part of the control arm) can be dangerous in addition to the above.