Curious what made you go this route rather than say a more full featured framework (Django/Rails)? Just based on assumptions, was it the ability to specify each of your preferred components?
For me because jinja2 is better than django's templates, sqlalchemy is also better than django orm. And you can use them as separate (sqlalchemy on desktop app), blueprints also (for me at least), everything is not tied to the sql-orm so you can use nosql to webscale.
the long answer is, a combination of many things: - flask is simpler, has almost no learning curve
- Django's ORM is not great, and I preferred nosql where things can be done faster and no schema migration was needed
- Jinja2 seemed better and the template structure was simpler, and the static file serving seemed more straight forward in flask
- settings management, urls and routing (with decorators), blueprints and many other things ..
I really believe that Flask represents the best way to design any web framework.