If you don’t need the larger volume of lookups then there are only three reasons to stay on a paid plan. These are:
If you require the ability to make API calls to the Addressfinder database.
If you are using Addressfinder on a non-public facing webpage or CRM.
You prefer the peace of mind in not having to worry about exceeding the lookup limit of the free plan.
Direct API calls and non-public facing usage is not permitted on the free plan.