This is a hold over from 3.5. in 3.5 every creature has the option of just taking its species level. It's uncommon for humanoids to advance in type levels because class levels tend to be stronger. Though I have build 5lvl commoners without classes in some really tough area. I also had a random farm hand just be a level 20 humanoid for fun. Also note that creatures (mostly humanoids) that only have one hit die can substitute a class for their race level.

The tabaxi on d20pf is level 2, and then multiclasses into whatever you like, but unless you are planning a low skill, combat focused, non flanking rogue you are probably be better off going cat folk and getting better class advancement and skills. In pathfinder tabaxi live far from "civilization" and are more beast than person this is why they are all born "stronger" than the civilized catfolk.

Comparing tabaxi to cat folk assuming all 10 for stats before adjustment

1 rogue tabaxi (lvl 3 character).
Climb 20ft,
Dark vision.
1 damage, 1 atk, 1/lvl HP (3),
All weapon proficiency (will replace claws.).
bite 1 attack/round. ( 1 damage avg).
Rake 2 attack during grapple or charge. Can't use weapons ( 4 DMG).
Pounce. Full attack on a round you charge.

3 rogue cat folk (lvl 3 character).
12 skill points.
Low light vision.
1 perception, stealth and survival.
1d6 sneak attack.
Trap sense
Alternate racial traits.
Favored class bonuses.