It seems increasingly popular for laptop manufacturers to preinstall the 64 bit version of Windows 7 on laptops. Whilst there are well understood benefits of 64 bit OS over 32 bit, how much of that is realisable on a laptop? What is the real advantage of 64 bit OS when the hardware otherwise limits performance by the capabilities of the RAM slots and hard disk data rates?
Since you've hinted that you've understood the benefits of 64 bit OS's, I will not elaborate on this aspect. One other reason is to do with Microsoft moving to ensure that eventually all their OS will be only 64 bit.
One big step is that their Windows Server 2008 R2 is only available as a 64 bit OS. If Microsoft, with the help of laptop manufacturers can get all their users to migrate to 64 bit OS's when both options are available; then when they release their '64 bit only' Desktop line of OS's in the future, the market (with users on Desktops and Laptops) will receive it with little or no resistance.
quite simply, laptops have started having enough ram that it matters, and more importantly, drivers for 64 bit systems have matured to the point where its viable.
Even where there's models with less than 4gb of ram, using 64 bit means they only need to support half as many variants of the OS , and can offer upgrades to available ram with less hassle.
It really breaks down to market forces more than anything else
Since their processors are 64 bit... why not using the right OS (64 bit)? There are many advantages of using 64 bit OS in certain conditions and most of the new laptops will comply in a very near future (or be upgraded for some older ones) while there are no advantages of using 32 bit OS so I would find strange a 64 bit machine to come with a 32 bit OS. This was done in the past because there were a lot of incompatible software and drivers for 64bit.
Anyways, is there any advantage of using a 32bit OS on a 64bit machine today?
Laptop computers began outselling desktop computers a few years ago so many people use them as their main work machine, sometimes hooked up to a docking station or at least a big monitor.
These people are professionals and want the latest. 64-bit OSes have now been around for years and are no longer bleeding edge. Even netbook CPUs are 64-bit now. So it looks like the manufacturers and Microsoft have decided that 64-bit is the future as of now.