Cabin crew age is a reflection of the demography of US employees. Have you aver looked inside a US cockpit? Many FOs have completely white hair and it looks like they will soon retire. The point is that US hasn't been growing as a company in years, and most employees are survivors of the post 9/11 furloughs. That is one of the biggest financial problems with north American carriers: even when they've fired all the less senior people, and cut salaries, the workforce is on average very senior and paid at the highest levels of the seniority scale. In general, keeping labor costs down requires growth, or at least a balanced workforce in terms of seniority, so that the average salary in not too high on the scale.
If you look at a LH longhaul flight, you always see a veteran captain and a young FO (in his thirties). That's a perfect balance. On many carriers in the US, everybody is old. One day these airlines might even have problems replacing personell as the old generation retires at once.