He was no mere tourist—He “made His dwelling among us,” (John 1: 4). The word translated “dwelling” is also used for the tabernacle in the wilderness and is meant to remind us of such. God didn’t desert His people in the wilderness! In fact, He was there in their midst the entire time. In the same way, Jesus didn’t come to earth for a weekend retreat, He came to live among us. Even when He physically departed, He sent His Spirit to be a token of His presence (John 14:18ff).
And there’s glory in all of this. But then that’s not a surprise because there’s glory in the birth of every child, isn’t there? Although strictly speaking birth is a “natural” event, you’d have to be blinder than Samson not to see God’s fingerprints all over it. The new life you hold in your arms is from God. It is innocent and pure—without the stain of sin. And although Luke’s account seems to have this kind of glory (and more) in mind, it doesn’t seem to me that’s what John is after when he says, “We have seen His glory,” (v. 14). He wasn’t there at the birth so he’s not giving witness to that. It makes sense that he’s after something else.
I think the glory he’s speaking of is the glory of God living as man, the glory of One who is full of grace and truth and as such, reveals God in a way that no one before or after has done or can do (v. 18). This is tabernacle glory and more. The glory of the tabernacle was that God was dwelling among men. The glory John beheld was God living as man.
This fits with what’s happening as John is writing his gospel. Toward the end of the first century an early virus of what will later be known as Gnosticism is infiltrating some of the churches. Unable to reconcile the spiritual with the material, it holds that all material things are evil and all spiritual things are good (and incapable of evil). Because of these premises, they decided that Jesus didn’t come in the flesh—He just appeared to be in the flesh but was like a hologram or phantom (Docetism), or that the spirit of the Son of God entered the carpenter’s body at his baptism and departed at the cross (Cerinthianism). John will have none of this. Christ not only came in the flesh—it was as a man that He fully revealed God.

In John’s gospel then, there is no nativity scene per se to celebrate Jesus’ birth (although he would hardly be against that), but there’s the glory of revelation — the Word becoming flesh and through that life revealing God intimately and ultimately. Celebration is always appropriate; but celebration through transformation is what really brings Him glory.
May the word become flesh in all of our lives!