Because Google has not yet approved your organization's card. Google reviews every organization before members can add a card to Google Wallet. A card issued before approval would be stamped TEST ONLY, so until then Android members are not shown an Add to Google Wallet button.
Org admins can see where you stand under Organization Settings → Membership card, in the Android — Google Wallet row:
- Not set up — 2Labs has not yet set your organization up with Google. Ask 2Labs to start.
- Not yet requested — 2Labs has opened your account with Google but has not yet asked Google to approve it.
- Waiting on Google — sent to Google for review. The page shows the date it was sent and the date it is usually back by, two working days later.
- Live — approved. Android members are offered Add to Google Wallet.
Apple cards do not depend on Google's review.
Members who want an Android card during the review are recorded and emailed a link to add it automatically when Google approves. Only members with an email address can be emailed. You can see them on Members → Membership cards under the Waiting on Google tab. There is nothing for you to do.