The abilities are designed to be "fun" and not a chore. Using the abilities is expected to be a choice for advanced players, but not necessary for beginners. Players are supposed to want to use them to get an edge over opponents, but it is possible to beat an opponent without using them.
Dustin Browder declared that the economy must have an important part of the game.
↑ 3.03.1No auto cast for Mules or Obelisk (new name for Dark Pylons), or for the Queens ability to spawn Larva for that matter. The thing is, these abilities can be used optionally and using the ability costs energy that you could also use for Scanner Sweep or the extra supplies on the Command Center for example or for the Obelisk loading your units with energy. So using this ability to get extra resources should still be a choice.
Also, as already mentioned, this is an option that advanced players can use to really get ahead in the game, it is not necessary to enjoy the game as a beginner. Still when you have a couple of expansions, you can really see that you got to pick up on your game to really fully take advantage of these features, especially if you have battles or harassment going on at the same time. Xordiah. 2009-07-10. Mule/Dark Pylon... do they auto cast?Battle.net StarCraft II General Discussion Forum. Accessed 2010-01-30.
↑The Macro mechanics are still present in the current build. Concerning their purpose, it is to change the gameplay a little bit. They are very useful and we try to make them as useful as possible, so players will want to use them, but also will enjoy using them. We do not want them to become a chore, but rather be a certain extra something for the player to think about while playing.
Talking about changes and updates: Which build are you referring to? ;) As you already know everything is subject to change and the dev team is constantly changing things to make the game as balanced and fun as possible.
For me personally the coolest thing is the Warp Gate. You need to get used to it, as it is a big change compared to SC:BW, but it is extremely useful and being able to warp in units in close proximity to pylons gives you a lot of different strategic options.
Is it necessary to use them, to be competitive? Well this answer is a cliché, but it depends. The purpose of using macro mechanics is to get an edge over your opponent. It is possible beat another player without using different macro mechanics, but it helps quite a lot to use them :)
About cooldown times: In the current build they are only limited to the amount of energy you have to spend. Kapeselus. 2010-02-02. Macro mechanics questions for blues. Battle.net StarCraft II Gameplay Discussion Forum. Accessed 2010-02-02.
↑Gas doesnt [sic] HAVE to be more interesting, but economy strategy and economy management must be an important part of the game. We have tried at least a dozen different gas systems in the last few months as we have explored what works and doesnt work inside StarCraft game play. We will continue to work on different ideas for a new gas mechanic until we find something that meets our needs or until we discover that all possible solutions are worse than what we currently have. What was shown at WWI was very much a work-in-progress Cavez. 2008-08-14. August Discussion Topic: Gas Mechanics. StarCraft II General Discussion Forum. Accessed 2008-08-21.