Your shoulder is the most mobile joint in the body, but also the most unstable... Especially after years or decades of repetitive reaching and lifting.
It's supported completely by thin ligaments and small muscles. And when these get tired or injured, your joint starts to "drift", which leads to clicking, grinding and aching.
Left unsupported, that drift eventually leads to an even worse injury, like a tear... Unless you find a way to provide the joint with the proper support it needs to handle the daily grind.