From my point of view, regardless of whatever career you want to go into - a degree is a must.
From an aviation career perspective - in particular, the role of an airline pilot - I doubt that a 3/4 year degree (in terms of subject matter) - is going to make the difference between whether you make it or not.
But a degree offers you something, which, unless you've done it - you can't really comment upon.
We leave home (some of us - for the first time) - and learn to cook / clean (some of us do) / wash / iron. The important word here is that you develop some independence.
You've got to engage in some study at some point during the 3/4 year course. You learn self-discipline.
For those that decide to take their degree seriously and refuse to spend 3/4 years p*ssing it up against a wall - you also have to work bloody hard and occassionally make a few sacrifices to study when you'd rather be out having a bit of fun. Of course, here you learn to prioritise and show forward thinking
These skills are all extra-curricular, and usually form just a small part of actually learning something to do with your subject.
You grow up a lot between 18-22 - and your situation and responsibilities change. Your attitudes and goals can change - and you have a much clearer idea of a) Where you want to be, and b) How you're going to get there.
If I was to advise any young(ish) person of 16/17/18 years of age who was serious about becoming a pilot - I would advise going to university first. There's jobs out there now - they'll still be there in 3 or 4 years time. University is not just about a subject education - it's about a life education - and it will prove priceless in years to come.