Theres a point to all that, didnt you listen to the Gman when you first played the game? Didn't you read the intro with all the meteors hitting each other? If not here:
It was written in the ancient scrolls of Xian, that during the last
Crelat of Xen time, a portal would be opened between two universes
and a being would cross the void and cause the second re-birth of
Nihilanth, and that all Xen would be drained of their lifeblood, their
knowledge.
And that, in this time, the Xen race would be oppressed
by the armies from the far side of the portal.
It was also written that once the portal was opened, a human known
as "Freeman" would cross the galactic transverse into Xen space, and
set free the three sacred Telnorps, the guardians of the gate who had
been captured from the ancient enemies of the Xen....
....the Zan from the Theldran galaxy.
And so it was that the prophecy came to pass, and the weakened Xen were
powerless to resist an onslaught from the Zan. In the dawn of the first
Ashaan of Xen time, the elders of the high council sanctioned an uneasy
alliance with the perpetrators of the impending disaster, the Human race,
in order to restore the sacred telnorps, and thus sealing the Zan gateway...
.....forever.
The ambassador of the alien Investigation unit on earth was called upon
to "redeem" the situation by employing the use of the very individual who
had inadvertently been the cause.
Get Half Life Model Viewer and listen to the Gman's speech, you'll realize why you are going from place to place so fast.