Planet Merkur/Óðinn 88 days around sun.
So: Óðinn, — always on the run–  has an eight-legged pony.

Sleipnir is – according to Óðsmál research – our human nervous system. His 8 legs refer to the 192 nerve-endings.

When we transcend, we travel on our vehicle Sleipnir, to and fro, from Miðgaður to Ásgarður. No big deal, man, as Ásgarður is here right within us.  From me to me !!

No pony is of any use to us if not trained to become smooth and sleek and willing.
Sleipnir is the sliding, the slippery, and we train him sweetly.

—  Nervous system a vehicle !!!  I simply love the allegory and symbolic language in our myths. —

So, Q: why would we go into the trouble of visiting Ásgarður when we have everything here in Miðgarður: food, sex, fight and flight responses, money and work? Suffices?

A: To shovel the divine perfection of Ásgarður into our higher brain, human brain. Train our nervous system to function adapted to both realms.

We go to and fro to — in time — to be able to maintain the perfection gained, while vigorously acting in life. Our forefathers term that ability as fimbulrúnir (the most powerful secrete runes displayed).