Sure, in many cases the dev's computer is powerful enough to handle that.

However:

• The more the dependencies, the more likely it is to pull-off a supply chain attack. Any of those thousands modules can be compromised and infect either the user or the developer.
• Not all computers are optimized for working with so many tiny files. Have you ever worked in a company that uses McAfee Antivirus? Even Defender can be a massive performance hit in some cases.