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)

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.