As a matter of fact they do, the ones in the blocks are either 1/2 hour ahead or behind the zone time. IIRC, India is +5 1/2 not 5...
as for the bent lines, they encompass island groups or areas to keep them consistent within a geographical area. If you were to use strictly longitude as the seperator then you would change time zones every 15 degrees.. that would suck if your home was at 75 degrees west and your neighbour down the street was one hour behind because he is at 75 degrees 1 minute 1 second west
For a detailed list see here...
http://wwp.greenwichmeantime.com/info/timezone.htm