Why do I need to collect payments myself when connecting to Vrbo (via API)?

Short answer

It is a Vrbo requirement.

Slightly longer answer

Although Vrbo takes payment on your behalf when managing your listings directly on their platform, they require you to take payment yourself when connected via an official integration partner.

Is there an alternative?

At present there is no alternative.

Do I need a Stripe account to connect to Vrbo?

Yes.