I read once that if you ever wish to know if your SO is the one for you or not, the best way to find out is to travel together. As the others mentioned, traveling can expose the good and the bad in each other. Admittedly, traveling won't be the 'ordinary life' when you settle, but just like in regular life, there will be pressure. Some pressure can surface while traveling. How well you guys will agree on a budget can be tested during your days on the road. In your traveling days, you'll see your partner's money management skills as well as how you deal with unfortunate situations.
Outside the test, humans are social beings. Any experience won't be as great if not shared. As for people like me without SO, you still make the most of your travels even without partners. One's life status should not hinder one from experiencing the world.