Why Hovers is so slow?

In logic way, they must be fastest land units, cause they HOVERs above the ground. They got zero friction with the environment, they fly like a plane but on ground altitude.

Your 'logic' is called 'fluff' and is not how we balance, but irregardless, hovers do happen to be the fastest land factory, they were designed that way.

Here are some comparisons:
Mace 2.2 vs Leveler 2.0
Halberd 3.2 vs Ravager 2.95
Hovercon 2.8 vs Vehcon 2.4
Scrubber 4.8 vs Scorcher 3.7
Penetrator 2.4 vs Impaler 2.25

The only criteria on which vehicles are faster are the Dart, which is 5.09 (not much faster than the scrubber which costs 2x as much), and the Scalpel, which is the slowest hover at 2.1, but it's a skirmisher which benefits greatly from the speed it does have and has no direct comparison in the vehicle factory.

I appreciate the opportunity to illuminate our design decisions to the playerbase in this way but if you are going to make posts like this you need to at least check whether your basic fundamental assumption is even accurate.

In real world: hover can be fast and move on water but it can't turn!

F1 racer can turn, tokyo drift can drift, but hover cannot!

Hover will just slide and make silly mistake like bumping on other hover for example.

quote: * sand doesn't have hills

True, true….but what about sand dunes?

Also, sand may not have hills but hills can definitely have sand

Irregardless is technically a real word, albeit only because so many people suck at their own language and hacked together irrespective and regardless. Some more examples of words changing over time:
Gay
Decimate
Its vs It's

and as a bonus, the massive confusion between: e.g. vs i.e. !!!

mackey
http://en.wiktionary.org/wiki/i.e.

not sure how they managed to the "in effect" from i.e.
(silly americans)