Technically they do, per Yoda: "Confer on you the level of Jedi Knight, the Council does."

If you're talking about an actual knighting ceremony sequence, then sure, but that doesn't change the ending, just adds better payoff for other moments throughout the film when Qui-Gon praises Obi-Wan's skill.

I think Lucas was just going for that grand celebratory ending akin to the original. To a certain degree, it was what the audiences might have been doing in 1999 lol

The opening crawl already calls him a Jedi Knight, which is weird.