I think there are many skills learned as a MT major that make you as marketable as many other majors. Yes there is true vocational training in college, but I would not put a general business degree in that category. Accounting yes, but management or marketing no. So an MT major can fare just as well in the job market as a history, English or poli sci, or communications major, and can certainly pursue grad school at a later date.
The biggest difference to me is the choice one makes in terms of whether they want a 9- 5 job or whether they want to have flexibility so they have the time to audition, rehearse and perform. If performance is the goal, then they are going to be on less of a career path with their day job, and tend to take jobs like working in restaurants, babysitting, etc, so that they have more time to pursue their performing career. With luck, some of these cash making jobs can still involve music and theatre–like being an accompanist or directing school shows.
But once you have a degree, you can change paths when and if you want to. So one can chose 5 or 10 years down the road that you no longer want to be a performer in theatre, and can still use your degree to find a job or enter graduate school.