German Birthdays: A Quandary for the Uninitiated

North Americans tend to be startled by German birthday customs: there's no such thing as the birthday boy or birthday girl. If you want a birthday party--or worse, are expected to have one--you organize it yourself. You also invite all your friends and co-workers. Plus, you get to pay. You get to bring piles of sandwiches or boxes of cake to the office, at the very least. A German friend and I share a birthday. I tried to phone her to wish her a happy one, but had to go through three or four friends, all of them uncertain whether they were allowed to reveal her hideout, before I finally located her in the hotel where she was taking refuge . . . in Switzerland. She and I had a good laugh. She was having what the Germans call a "round" birthday, which for them just means a birthday with a zero at the end, marking the end of one decade and the beginning of another. Those are the birthdays on which some amount of flair is dictated by German culture. You either hide out and hope no one knows you're having a birthday, or you throw a massive bash. For her, the thought of having to invite fifty people to a restaurant--or cook for fifty, or more, at her own home, all at her expense--was something she could not face. She'd rather hide. I've also adopted a policy of hiding on my birthday, since the thought of a huge spread catered by me on that day literally makes me burst into tears. I have quiet birthdays with my husband and our kids, and I dream of past glories, when a friend or two, back in that palace of perfection, New York, would take me out to a little restaurant somewhere and not let me pay because it was my birthday. Because you'd never dream of not treating someone on his or her birthday.
Recently, my husband and I were stymied by a birthday invitation we got . . . and didn't get. German friends who came to our wedding, whose family always got together with ours,  whose son's wedding we attended, one of whom is our oldest's godmother, whom I look forward to seeing. . . these folks issued a birthday invitation for a round birthday. A rather important round birthday. But to my husband's consternation . . . the wife called him . . . they were only inviting him.
"Yes," he said, puzzled, "I had been thinking it would be fun for you and me to go, and the children are old enough to manage on their own for a weekend." But the wife had used the singular term for "you"--she'd been quite explicit. Stunned, I wondered whether the husband just didn't want to feel like he had to speak English on his birthday--if I'm there, they do tend to speak English for my sake. Then I wondered if this was a guy's night out. Then why would the wife do the inviting? They don't have enough beds? I can't come up with a good reason for this. My husband's going because he's loyal to his friends, but I think I won't feel the same way about these folks after this.