Why such differences between Infopath 2010 templates for a Form Library and for a List?

Question

Table 3 (Comparing form library and list templates) of msdn article Building SharePoint Applications with InfoPath 2010 (Part 1 of 2) states that:

• support for custom code is available for a Form Library Template but not a List template
• Infopath Filler as offline client is available for Form Library template but only Sharepoint Workspace for a List Template
• digital signatures are available for a Form Library Template but not for a List Template

Why?

I'd like to understand under-the-hood things better for and before making decisions in selecting and using the right Infopath form template for my tasks.