I've been encouraging DD to do it for years - just simple things like cutting off jeans, trimming with ribbon, adding studs/gems, etc. And she's only 11yo.
But my mum is a fab seamstress and so I've grown up with not just accepting as it is, iyswim.
Unfortunately good haberdashery is quite hard to find. Perhaps Gok's influence will lead to a resurgence (and accessibility to nice dressmaking fabrics please - most shops seem to have more craft fabrics than dress fabrics).