Making Squirrels on entry and attack is solid, and being in green lets her access the token doublers that Krenko missed out on
Do you really think people are willing to waste their Abrade on a Simic Signet when it could potentially stop an Orcish Bowmasters or a Portal to Phyrexia
Urza, Talrand, Baral they never want to be turning sideways, and so getting the best part of protection with the option of paying more for a 4/4 token with relevant creature types
You sacrifice flying creatures but you get to do more things with your own creatures on your turn, and bouncing cards of theirs with Man-o'-War and Tradewind Rider could deal with things you don't want to give to other players but don't want the original player to have, either
And each time you increase that loyalty count, you have a better chance of getting a powerful 2nd ability to work
Once you begin to cast The Indomitable from your graveyard, it doesn't matter what happens to the tapped Pirates and/or Vehicles you control