Just tossing this up as PART of the reason that Ive already touched on.
Now the birth of Jesus Christ was on this wise: When as his mother Mary was espoused to Joseph, before they came together, she was found with child of the Holy Ghost.
(Mat 1:18 KJVA)
espoused to Joseph
and thereby the outward credit both of Mary and Jesus were secured; for had this appeared before the espousals, the Jews would have fixed a brand of infamy on them both; and both the espousals and her being found with child...
-John Gill
Exposition of the Bible
The Jews were all over Jesus because they knew the earthly parents of Christ.
Had they even THOUGHT that Christ was born out of wedlock there is no way that that accusation would not have been used against Him...and Mary for that matter.
Additionally, Jesus genealogy is traced thru JOSEPH, not Mary (some claim she was descendant of David too, but it doesnt matter for this point).
The Jews were obsessed with genealogies and it is thru the male that this is traced, not the woman.
Of course, if anyone has proof that that is false, Id like to see it so I can amend that particular note (that lineage is traced thru the wife)