For the Spring’18 release, Salesforce has introduced 2 new options for Lead Settings.
The first new option includes “Don’t Create an Opportunity”. Below will show you how to enable this option:
Select “Don’t create an opportunity” by Default in Covert Lead Window
When this is enabled, the “Don’t create an opportunity” checkbox will be checked automatically during conversion.
This could save your sales rep time to check this if no opportunity is required most of the time during lead conversion.
The second new option includes “Hide Opportunity Section of Convert Lead Window”.
When this is enabled, this will hide the opportunity creation section in the lead conversion wizard.
Please note that the options above are meant for lightning experience users only. Also that these are org-wide setting, they cannot be determined which user to disable/enable.