Carrier roaming is usually the most expensive way to use data abroad. Here's the math, plus when roaming still makes sense.
Local-grade data prices in 150+ countries. Same network as locals, none of the roaming markup.
Convenience: you don't have to install anything. But you pay 5–20x more than a Simline data plan in the same country.
Carrier roaming is the easy default, and the most expensive choice you can make. Spend two minutes installing Simline and pocket the difference.