To some I’m preaching to the choir. To others (the ______ only guys) I’m dead wrong.
Let me start by same no tool is an absolute must have. You can get very strong and in shape in many different ways. However, if you want the full package then you need to train with a barbell.
The barbell is designed to be lifted. Weight is to be put onto the bar and the exercises are done with it. It serves no other purpose. Because of its design you can lift the most weight with it.
While you can do single arm lifts with a barbell (one arm snatches and getups are fun!), it is primarily used with two arms or legs. This means the full body is behind every move. This is best for big compound exercises like squats, deadlifts, presses and rows. Especially in squats, nothing comes close to the barbell.
Now you don’t want to exclusively use a barbell as you need to do single arm lifts with dumbbells, kettlebells or other tools. Have you ever watched a guy that goes to the gym and lifts barbells, and probably uses machines too, try to press two kettlebells at once? Usually because of imbalance one bell goes up and the other, if it goes up, takes much longer to get there.
The barbell can be used for partials, but that’s another article itself.
With weight plates the barbell can be incrementally loaded to whatever weight you need. This makes the easiest form of progression possible. Only dumbbells also have this ease of progression. Kettlebells make a big jump in weight. Bodyweight you have little choice except to change the leverage. So instead of locking yourself into certain weights you can slap on 2 ½ pounds (or less if you have fractional plates).
Now the barbell may not be the best choice for every move. Having the locked in, hands pronated path for overhead presses doesn’t feel best for me. (I’ve heard a log bar is great but do not currently have one.) But you don’t have to do any move that doesn’t work for you. Just use the barbell on those that do. For certain moves it can’t be beat.
And since a barbell can be bought for cheap, and even a crappy one will last you a long time, you own it to yourself to even if you train in a home gym. Just that and a few hundred pounds of plates and you’re in business.