Do you need a scale when you smoalk some dmt? Not really. You can eyeball, you can experiment, you can get the hang out of it and not have too many problems, just the occasional crazy trip. Not too bad.
However, when you decide the make some changa, or some ayahuasca, or some anything else, you're going to need that scale! Eyeballing a 1:1 by weight pile of dmt and caapi leaves isn't easily done, and I doubt I could've seen the difference between 2 and 4 grams of mimosa when I first started brewing aya(logues), probably couldn't tell the difference now.
So... do you need a scale? Right now? No.
Might you want to look into one? That's up to you.