If you don't want to ask your clients to verify their email address when creating a new account you can. However, note that this means users can create accounts with nonexistent email addresses and be able to do bookings.
To deactivate email verification, go to the "Settings" page and select the "Deactivate email verification for new user accounts" checkbox which you will find right in the beginning of the page, in the "General" section. Store changes by clicking "Save" on the beginning or end of the General section.
When email verification is deactivated, when a client completes the "Create Account" form his account will be immediately ready, the verification token will neither be requested nor sent by email.
You can activate email verification again, whenever you like by unselecting the referred option.