Maybe I just fly a lot, but baggage fees are pretty clear along with limits.
For Spirit, baggage fees are also clearly listed here: https://www.spirit.com/optional-services
Depends on the website. Skyscanner include that kind of thing, as well as seat pitch, if food is included, etc.
It’s irritating but it’s not the airlines responsibility to support the comparison sites.
Many people just pick the cheapest price on cheap tickets or something (which is usually spirit. They famously charge so much for baggage that they end up being more expensive than other airlines)
I don’t understand these comments about how it’s confusing. It’s all quite clear.