So basically either the number of tourists is deliberately nerfed (for performance?), or there is a bug preventing them from showing up. But even with an attractiveness of the max 100, tourists show up in anemic numbers. For example I have a city of 1.2 million. It may see between 300-800 tourists total, which is an incredibly small number for a city this size for all the attractions.
The problem with this is that it's the tourists who would presumably be patronizing the hotels. So frequently the hotels have almost no occupancy. Take this specimen, even with a -1% subsidy for lodging.
Steam Community: Cities: Skylines II. -1% subsidy on Lodging, well at least there's 126 people getting rooms here. I am hoping I don't get 5/5 disease in Comm with no tax.
steamcommunity.com
The hotels will continue to fail and the businesses in them will churn and put people out of work. Note that this hotel has 1,017 employees. The business eventually collapsed because there wasn't enough demand for the business. I am sure this behavior changed because originally tourism worked in the game.
The knock-on effect I suspect is that it will hurt demand for the food sector as well. There could be other issues that this could cause, but I expect there'd be a general lack of potential income from tourists.