Forgive me if I'm repeating much good material already shared here.
Even a 3 element yagi should have a pretty good front to back ratio, but as others have noted, if you're close, and/or the signal is very strong, then you may not see much (or any) difference. Attenuation is a great way to "expand the scale" and make use of the dynamic range of your signal strength meter, or even detection by ear. You've got to reduce the signal enough so that it's very small when not pointing at the transmitter, allowing you to actually see the difference as you point it in the right direction.
If you're interested in an alternative to the Arrow offset attenuator, I've been using the
K0OV offset attenuator kits for amateur radio fox hunting for years. If you're okay doing a bit of the construction yourself, these work well.
I know that some here will say that signal strength meters aren't all that important, but I disagree - it's an important component of effective direction finding, and you're missing out if your radio doesn't have one.
Another point about a beacon like the BRB: if you're swinging your beam antenna around, trying to get a bearing on the signal, but the transmission is short, then you've just barely got any direction information before the signal's gone. One of the great things about the BRB is that it's programmable, and you can change the duty cycle (on vs off timing). Sure, the longer the transmission, the shorter the battery life, but I've found a compromise that provides a longer transmission that's easier to DF, and still maintain a battery charge life that's many hours long.
This stuff may not matter for those who are flying in an environment that allows seeing the rocket on the ground before getting really close, but if it's in tall grass, crops, trees, etc., you could be almost on top of it and not see it - and that makes these DF tools like signal strength meters and attenuators much more valuable.
Mark