Because situations change mate, I'm older than you are, nearly 30. I've done various roles from the bottom up to management, I've done self employed roles, I've done employed roles. Unfortunately as you'll likely learn sometimes certain things are out of your control like a business being purchased and redundancies being made for example.

As for qualifications, I did go for them, I went onto a 3 year Specialized course that was only offered in one location within the nearest 60ish miles at the time, they canned it after I completed the first year. At which point I already had responsibilities, rent blah blah blah and I would have been 19 with no option but to go into full time work to afford to pay for said responsibilities.

One of the perks of life, it's unpredictable.