TL;DR; The VS2010 ISO is small because it excludes MSDN documentation, which is not yet available offline; users can access documentation online instead.

The reason is simple, it has no MSDN documentation in it. I for one never install the MSDN documentation and just use the online version and have always found it a pain to have it inside the same installation, but may people find it useful.
And, why is there no Offline MSDN documentation? The answer is simple, it is not ready yet…
Technorati Tags: ALM
If you've made it this far, it's worth connecting with our principal consultant and coach, Martin Hinshelwood, for a 30-minute 'ask me anything' call.
We partner with businesses across diverse industries, including finance, insurance, healthcare, pharmaceuticals, technology, engineering, transportation, hospitality, entertainment, legal, government, and military sectors.

Brandes Investment Partners L.P.

Higher Education Statistics Agency

Slicedbread

Capita Secure Information Solutions Ltd

Genus Breeding Ltd

MacDonald Humfrey (Automation) Ltd.

Microsoft

ALS Life Sciences

Freadom

ProgramUtvikling

Kongsberg Maritime

New Signature

Ericson

Flowmaster (a Mentor Graphics Company)

Bistech
NIT A/S
CR2

Cognizant Microsoft Business Group (MBG)

New Hampshire Supreme Court

Nottingham County Council

Washington Department of Transport

Washington Department of Enterprise Services

Ghana Police Service

Department of Work and Pensions (UK)

Lockheed Martin

Akaditi

Kongsberg Maritime

Flowmaster (a Mentor Graphics Company)

DFDS

Graham & Brown