Absolutely not. But of course you can use it if you prefer, see Can I use my own carrier contract with pre-negotiated rates?.
The label platforms we integrate with have ready-to-use contracts for a variety of carriers:
See here for a list of all carriers: https://easypost.com/carriers/ and supported service levels https://www.easypost.com/service-levels-and-parcels
Ready-to-use discounted rates for:
USPS
See here for a list of all carriers: https://goshippo.com/carriers/
Ready-to-use discounted rates for:
US Domestic
USPS
UPS
US International
USPS
DHL Express (US outbound)
Europe
Deutsche Post (Germany)
Parcelforce (UK)
Australia
Fastway
Sendle
CouriersPlease
See here for a list of all carriers: https://www.shipstation.com/partners/integration/carriers/
Ready-to-use discounted rates for
USPS (Stamps.com)
UPS
Asendia
Hermes UK
Parcelforce