Recently, I noticed people taking to Twitter to offer their two cents on restaurant seating policies. Namely, is it okay for them to make your party wait until everyone else arrives?

If you’ve never been a server or line cook, this policy probably seems unnecessarily punitive because it appears to punish the people who bothered to show up on time for the sins of the people who didn’t. However, if you have worked in the restaurant industry, you know this policy isn’t only wise... it’s also just. Why? Buckle up, I’ll explain.

First, imagine you’ve made a reservation for a party of eight at a bustling Portland restaurant for 7 pm on a busy Friday night. If most of you are late, and the host nonetheless seats your party, you’re taking money away from your server.

I know, I know. Hear me out. Let’s say you’re all going to wait for your last tardy tablemate to be seated before everyone orders their main courses. If it takes that last person a whole hour to show—and believe me, that happens more often than you’d think—you’ve all unknowingly committed a restaurant etiquette misdemeanor: You’ve wasted an hour of your server’s time by fumbling over cocktails and sodas, and have likely robbed them of potentially squeezing in two extra four-tops before their shift comes to an end, because it’s very likely that you’re not going to settle up until right before closing time.

To put it in terms of cold hard cash, your collective tardiness just robbed your server of maybe $80 in additional tips. And if they share their tips with the bussers, servers, runners, hosts, bartenders, and line cooks, you’ve inadvertently stiffed them, too.

Second, the reason this rule exists is because things like this happen all the time. Restaurants had to invent it because if they hadn’t, your fellow stragglers could easily throw off the rhythms of the floor. The kitchen, the food, and the service at tables other than yours would invariably suffer, as well.

Kitchens are regularly clobbered on busy Friday nights. By the time your 7 pm reservation finally places its order an hour later, that kitchen might also be simultaneously cooking up the eight mains for the eight-top that did show up on time.

In other words, your tardiness can affect how quickly—and accurately—the kitchen will be able to turn out your food, and everyone else’s, for the next hour or so.

Still, with all rules there are exceptions. If you have a reservation for eight, and six of you show up on time, a good host will seat you. Five? Maybe—if you’re nice and your host is nicer. But don’t expect to be seated when just four of you show up. If there’s space, the host will seat you at the bar, where you can sip a cocktail while waiting for your friends. But if the bar is full—it’s 7 on a Friday night, after all—you’re going to be standing by the door until at least one other person shows up.

In other words, the rule should be flexible and your host should use discretion when enforcing it. But it can be wielded clumsily, too. The Mercury’s food critic, Andrea Damewood, recently lamented that she was once forced to wait until the rest of her party showed. The rest of her party, though, was her husband who was simply parking their car.

Enforcing this rule for a two-top is an unbelievably rookie move. Either the host was poorly trained and didn’t know they could rely on their own discretion or didn’t have the insight to relax the rule. Or worse, they were flexing simply because they could. Plus, that kind of move also punishes the server, who’d be more than happy to have Andrea running up a bar tab while she waits for her spouse to arrive.

In the end, though, it really just comes down to showing up on time, and five or six of you should be able to do so. It’s not that hard.

Oh, and don’t forget: It’s likely your server will only split your check up four ways, and possibly just twice. And don’t complain, because there’s a very good reason that policy exists. Lucky for you, I’ll be exploring that topic—and many more mysteries of the restaurant biz—in future columns.

Until then, happy eating and tipping!