Yes, because that's the antithesis to praying for public show. But this is not a command that the only way or place we can pray is (1) in our rooms, and (2) with the door closed. Prayer is how we communicate to God, not how we show off our spirituality to the crowd so they think highly of us. Jesus himself prayed in public (Matt. 14.19 and Matt. 26.36-46). It wasn't theater, but genuine conversation with God, and that's Jesus' point: leave the theater behind and talk to your Father. He's not giving us a command about a place to pray (gotta be in your room!), but about an attitude of prayer.

But Jesus does say (v. 6) "But when you pray, go into your room, close the door and pray to your Father, who is unseen."
It's the next verse, I suppose I should have included it.

Notice Jesus never says, "Don't pray in public." But it's "When you pray, don't pray as the hypocrites do." Jesus wasn't commanding his followers never to pray in public. The context of the passage (Matthew 6) is not to be a show-off. We don't do any religious practice for the roar of the crowd, but more for private motive and without ostentation. This isn't theater, but our relationship with God.

It's not that you can't give to the needy in some kind of public way, but don't announce it with trumpets (Matt. 6.2), just so that people think you're awesome. And don't pray in a public place just so people think, "Ooh, that person is SOOOO religious" (pious, godly, whatever accolade you want to shower on the person). I got the idea that this coach was just praying as a matter of course, not to be a show-off.

It's not like, "Oh, I want to pray. Oh, drat, I'm outside, I have to find a place to hide or be alone. Oh, no, where will I go???" That's not the point.

Then in the next verse (Matt. 6.7), he warns against babbling and prattling on like a big shot. Again, Jesus isn't condemning all repetition in prayer. He himself prayed 3 times in the Garden of Gethsemane (Mt. 26.44), and Elijah prayed 7 times for rain (1 Kings 18.43-44). What the warning is about is just being a big show-off.

I saw an article shared to Facebook about a high school football coach that is not allowed to pray on the sideline after a game. What is this even an issue when Jesus told his followers not to pray in public?

"And when thou prayest, thou shalt not be as the hypocrites are: for they love to pray standing in the synagogues and in the corners of the streets, that they may be seen of men. Verily I say unto you, They have their reward."