Well, I think tourists often choose cities based on what unique experiences they can offer. For example, some cities have famous landmarks or cultural heritage that you can't find anywhere else. Take my hometown Hangzhou - people visit mainly for West Lake, which has this poetic scenery that's been famous for centuries.
Another big factor is convenience. Cities like Shanghai attract visitors because they're easy to get around with good public transport and plenty of English signs. When I traveled to Jiuzhaigou like I mentioned earlier, the transportation was actually quite challenging compared to visiting a major city.
Also, food plays a huge role. Many tourists pick destinations specifically for the local cuisine - like how people go to Chengdu for authentic Sichuan hotpot. The combination of these things usually determines where people choose to visit.