The Sales CRM functions more as intended for lead capture from a web form where one email would be provided to create the contact record.
You're thinking in terms of the CRM as a Sales and Marketing tool, which it is, but it's also just a CRM: Connected to Gmail it's getting new records daily from people that have multiple email addresses. Moreover, just doing an import of addresses from other databases can result in multiple Contacts being created for the various email addresses someone might have.
Consider myself as an example, I have 12 different email addresses. When I take a new client or job, I'll have another. Those are 13 different records. They are all just me and each of those email addresses should be more easily uncovered as associated with the same person and merged.
What needs to improve
Today we have to go into a Contact records and use the Merge function to find the other emails and merge them. That's a manual process. A pain for large Contact databases.
The Contact list should have a "Find and Dedup" option. The CRM should find likely duplicates not based on the email identifier but other personal identifiers: same name, similar name in same location, etc. Flag those in the list and make it easy to check the duplicate Contacts and "Merge" them.
This really needs to be done as part of the platform as growing companies, teams with many people using Gmail as part of their outreach, etc. will constantly result in new Contact records that can go unnoticed as duplicates of existing records.