It's been nearly three years since Microsoft unveiled its "chat-based workspace" dubbed Teams - the Redmond giant's version of Slack. The firm also began the transition from Skype for Business to Teams, the latter finally replacing the former in August of last year. Even with all of this, Teams wasn't made available to all Office 365 subscription tiers, something which will change in early July.
Teams is currently the preserve of subscription tiers like Business Premium, but not lower tiers like Business (regular) or Professional Plus. Although the collaboration tool is being included in new installs of ProPlus, Business, Business Premium and Microsoft 365 Business, existing installs of the first two tiers do not have this yet.
Starting on July 9, Microsoft will begin a staggered rollout of Teams to existing installs in the monthly channel. Since this is going to take place over several weeks, not everybody will get it at the same time.
Another thing to keep in mind is that Teams auto-starts on users' PCs and will obviously be included by default in all installs. If you wish to change this behavior, you'll have to do so before deployment.