The default attire many audiences have in mind is the robe, with the color or something else denoting the type of magic or skill level the practitioner has attained. There’s no real reason for the robe other than cliché, but they do offer the chance to have an unknown quantity of pockets within, each holding ingredients for spells. However, other clothing can achieve the same; cargo pants come to mind, though the pockets are visible. Do we really need a wizard to hide how much stuff they’re carrying? Quick access to pockets during fights is wise, but a belt or bandoleer (used for bullets) can do the same.
Take a moment to question how practitioners are dressed and why. A robe could be considered formal and mostly worn while at official functions. Perhaps a shorter version is for travel, worn with trousers to cover the lower legs when it’s cold. A robe might be tradition or enforced on wizards in societies that insist on immediate identification (in this case, via clothing) of practitioners. Some wizards might wish to hide their abilities for any number of reasons.
Another old cliché is that wizards can’t wear armor. This may have been conceived to make such powerful characters more vulnerable, but we have other ways to do this. Armor interfering with gestures doesn’t make sense as a justification, given that sword fighting, for example, requires far more mobility. But another explanation is that metal somehow interferes with the wizardry; we can make such a factor true of one magic but not another to create distinctions, but it also seems that an enterprising person would fashion armor that doesn’t cause this, with such armor being hard to acquire.
Consider that the audience only benefits from a visual cue in visual mediums, so print authors have greater leeway to completely abandon all stereotypical garb. In other mediums, we may want an immediately recognizable style in our story world. Then we just need to establish it, which takes no more than a line of dialogue when someone comments on the outfit. In Star Wars (italics), we know who’s a Jedi knight at once due to inference.