Two-pocket jerseys are less common, but they can work well for the right rider. They're typically found on minimalist designs, some women's-specific cuts, and more casual jerseys. If you mostly do shorter rides or prefer a cleaner, less bulky look, two pockets might be plenty for a phone, a snack, and a spare tube.
The tradeoff is organization and capacity. With only two pockets, you'll have less room to separate items—so your phone might end up next to your keys or a sticky energy bar. On longer rides where you're carrying more food, tools, and layers, you'll likely miss that third pocket.
Consider a two-pocket jersey if you ride with a saddle bag or frame bag for tools and spares, freeing up your pockets for just the essentials. But if you rely on your jersey as your primary storage system, stick with the standard three-pocket design.