Simple, I'm 50+ years of age with deteriorating joints (mainly as a result of my 30 years driving for fedex), and most companies aren't interested in hiring someone like that no matter how exceptional their skill set. Believe me I have been looking.
I choose not to use the skills I have developed over the years just as fedex chooses to cut my compensation. The two items are now tightly interwoven in my view.
My stance is still the same. But now that you have revealed that you are an older gentlemen and a career driver. I would say having known a few with that many years. There houses are paid off, there 401k's are fat, there traditional pensions on point, and there new PPA's being prepared to be rolled over into immediate annuities to generate more monthly lifetime income. Some stock options. It is my hope that you have been disciplined enough to do some of these things as well.
The work you perform is an honorable thing. Make no mistake about it. You came in as a young man and when you do something long enough it becomes part of you. But follow me if you will. Your career has become almost like a Shakespearean tragedy. Early on brimming with love, pride, and passion. To have eroded right in front of you until it's current state present day. You are smart enough to recognize it, but are helpless to stop it or change it.
In my opinion the country is already in a pinch. All manufacturing and service jobs are outsourced or cut. Make the prospects lousy for anyone that hopes to have some semblance of the "American Dream". Pride for the worker. Loyalty to the company. It's gone to some extent.
Being in the mid 50's with joint discomfort is rough. And your right, companies aren't chomping at the bit to hire someone like that. The couriers we have retire recently after 25 and 30 years got Fedex to pay for a CDL for them about 18 months before they knew they were going to hang it up. Than they retired, and found work driving for private trucking companies. No touch on the freight. Just one avenue of approach.