Two points:
1. The opportunity costs for switching away are high. I suspect this comes into play in many areas -- say, emigrants to a new country who never develop a high functioning level of language skill (something I'll add applies just as much to English speakers abroad as those moving to English-speaking countries, if not more). And yes, there absolutely are exceptions, often many.
You're highly effective in using one language. You operate functionally at the level of a young child in another. Cross training to the new language is a massive investment of effort. Adult minds lose plasticity present in children, so the task is inherently harder. Plus you've got to do everything else necessary to keep going. It's a Red Queen's race.
Shifting tracks requires a very real sacrifice both in increased effort and reduced reward. It can be short-term satisficing to continue stretching out the lucrative current skill so long as possible. Situational awareness of that dead end may not dawn until late in the game as well.
2. Some skills are synergetic -- knowing one thing makes learning another easier. And yes, I see this all the time, particularly in metaphorical spaces. Thinking is I strongly suspect very much a matter of analogs, and collecting and applying appropriate analogs helps.
But ingrained knowledge is ... quite different. Changing handedness, or quitting habitual behavior (drugs, smoking, alcohol, gambling) is exceptionally difficult.
YouTube's "Smarter Every Day" has a great segement on learning to ride a backwards-engineered bicycle headset. Using gearing, the response of handlebars and wheels is reversed. It's all but impossible to ride this bike if you know how to ride a regular one, though you can learn, with sufficient time.
But: learning to ride the backwards bike makes riding a normal bike impossible. Until you've learned to context-switch between the two.
Fascinating bit of applied psychology.
https://m.youtube.com/watch?v=MFzDaBzBlL0