By adding plus one's to your guest list, your guest list could grow astronomically without even realising it!
If you need to keep a tight rein on your guest list, then only extend a plus-one invitation to:
👯♀️ a guest who might be on their own and not know anyone other than you or someone in the bridal party.
👫 guests who are married, engaged or in a relationship
TIP: to avoid guests thinking that they are entitled to bring a plus-one, be clear about who you are inviting on your invitation by clearly stating the names of each guest.