A (truly) portable application could easily be copied and used twice, while the companies much rather have people shelling out another xxx bucks for a license.
The biggest hurdle might be (again) the legal issues. Although you most likely get a no as an answer (knowing the tight legal space they operate in) it at least give the folks at Adobe a pointer that an official portable PhotoShop would be greatly appreciated by their (paying) customers.
Although legal issues prohibit us from providing you a portable version of PhotoShop, you might want to send Adobe an email requesting a PortableApps compatible version.
