Salesforce Lightning - Enable Shared Activities

Since Enabling Shared Activities in Salesforce is a feature that once turned on, it cannot be turned off, it's worth seeing how it will appear. The good news is that it works well with Lightning. Challenge is knowing the identify of the additional associated Contact records although they are displayed when you edit the Activity record.
Also shows how an Activity record associated with multiple Contacts can appear on reports - as multiple line items, each associated with different Contact records.

[robertjenkin]

Are there any reasons not to enable shared activities? Just want to make sure, given it cannot be reveresed.