Maybe it's because we know little of him and he did not have a leading role in the Bible. The last time we hear about him is when Jesus gets lost and that's all. The evangelists did not consider him important enough to even write when he died.
The real question IMO should be why Catholics venerate him so much.
This pretty much sums it up.
Troparion (Tone 2)
Proclaim the wonder, O Joseph,
to David, the ancestor of God:
you saw a Virgin great with Child,
you gave glory with the shepherds,
you worshipped with the Magi,
you received the news from the angel.
Pray to Christ God to save our souls!