Full Idea
We can distinguish at least two possible interpretations of Aristotle's thesis that eudaimonia is the chief good: either eudaimonia is that for the sake of which all action IS undertaken, or that for which all action OUGHT to be undertaken.
Gist of Idea
Does Aristotle say eudaimonia is the aim, or that it ought to be?
Source
comment on Aristotle (Nicomachean Ethics [c.334 BCE], 1097b22) by John McDowell - Role of Eudaimonia in Aristotle's Ethics §1
Book Reference
McDowell,John: 'Mind, Value and Reality' [Harvard 1998], p.3
A Reaction
It seems to me Aristotle is describing how people DO behave (they all want ot flourish), and then goes on to describe how they OUGHT to behave to achieve the end they all want. His theory does not describe convention, which mostly concerns pleasure.