In addition, "but" can coordinate a variety of elements, but "even though" can only comfortably coordinate clauses:

-- He is poor but happy / ?he is happy even though poor / Even though he is poor, he is happy.

Further, "but" can be conjoined with "not" to create "instead," and cannot be replaced in that case with a reworking with "even though":

-- He is not happy but sad.

Although this has a nuanced difference from the "but" we've been discussing, it still follows the general pattern: "A but B" or "not A but B" implies that A and B are typically in semantic or pragmatic conflict of some sort (although, as the first sentence in this post shows, it need not be a blatant conflict).

-- Paul

From: Mark J. Reed [log in to unmask]

"But" and "even though" are equivalent in force but not syntax - they
take their arguments in opposite orders:  A but B = B even though A.