Yes it does
Except if you don't use xDB or Analytics. In this case, VisitorIdentification is redundant.
What it does
It serves a number of purposes; but the most relevant to you is, it aids robot detection on your site. Sitecore (speaking broadly) functions like this:
- Assume a new visitor is a robot
- Send some code to the client via VisitorIdentification
- If the code responds as expected; assumes it's a real browser client
If you leave it out, Sitecore will assume all your visits are robots (crawlers etc) - and your sessions will time out after 60 seconds.
The robot detection component is enabled by default but to implement it fully you must ensure that you have added the visitor identification control to the layout of each page on your website.
Source: Configure robot detection functionality
And to ease your worry
Witnessed from this, not entirely pretty, piece of code driving this control.
<% if (Sitecore.Context.Diagnostics.Tracing || Sitecore.Context.Diagnostics.Profiling)
<!-- Visitor identification is disabled because debugging is active. -->
else if (Sitecore.Analytics.Tracker.IsActive && Sitecore.Analytics.Core.ContactClassification.IsAutoDetectedRobot(Sitecore.Analytics.Tracker.Current.Session.Contact.System.Classification))
<meta name="VIcurrentDateTime" content="<%: DateTime.UtcNow.Ticks %>" />