Some don't feel comfortable with their photos being seen by others without speaking to them first.
You are in complete control of your photos. You can choose to have your photos Blurred to all members. You can then choose to reveal your photos to a specific match at a time of your choosing (in the Chat tap the top right menu button and tap
Once unmatched or blocked your photos revert back to being Blurred automatically.
Both are optional however and are not recommended. Profiles with Visible photos receive 300% more matches and are unmatched less.
To change your Photo privacy go to
☰ Menu → Edit Profile → My Photos and amend the bottom option Private or Visible).