1. If you’re not travelling, you often don’t have a hotel. You could argue that working from home is also an alternative though. People looking for a WeWork may be trying to separate home and the office though, or escape distractions like children or roommates.
2. I could see doing this in your car for a short period, but not an entire day. It will get hot, cold or hard to breathe. Not to mention street noise.
3. Yes, though most libraries in major cities are full of homeless people, which makes it a hard regular option. It might work fine one day, but another day might be overcrowded. I’m guessing people getting WeWork are looking for some regularity.
4. Sure, again works for a day or two. Not a long term solution. No client will let you work there everyday without eventually charging you rent.
5. Yes, you can certainly do this for a couple hours. After awhile you gotta buy another coffee or lunch. It will start to get expensive. Also, doing this everyday in the same location may start to become weird or get you kicked out.

WeWork isn’t targeted at people who need an occasional office, but people that don’t have a traditional office building and need a regular, stable workspace.