I just did a search on that page on a couple specific time zones included in your list, and couldn't hit any results for: Caracas or Brussels. It doesn't seem you linked the right page?
As far as separate checkbox for daylight savings: (1) there are more rules than just daylight savings, and moreover some timezones have daylight savings other than 1 hour (this is rare but still); (2) most languages have libraries that will calculate the timezone for you, and it's both easier and more accurate, both for the user and the developer, to use these libraries to do all the heavy lifting for you.
As far as separate checkbox for daylight savings: (1) there are more rules than just daylight savings, and moreover some timezones have daylight savings other than 1 hour (this is rare but still); (2) most languages have libraries that will calculate the timezone for you, and it's both easier and more accurate, both for the user and the developer, to use these libraries to do all the heavy lifting for you.