Using only Leads whithout contacts

Using only Leads whithout contacts

I am planing to use just the leads modul. The reasons to ignore contacts  arefollowing:

1. By sync with Zoho Campaign I have to sync Leads and contacts and to send two campaigns not one.
2. The mobile app does not search in leads and contacts together
3. The field sync between Leads and Contacts is hard

I know that the potentials and invoices are connected with Contacts and may be I won't be possible to use them.

Has someone used zoho just with leads?

What other disadvantages could happen if I do not use the Contacts modul?