Actually, RAM IS the issue. It gets gunked up and locked down. How big is your swap file on those Linux boxes and your Windows machines? Android doesn't really have one, due to the short lifespan of the SD cards we use to store data on, which is part of the reason why we want a fully-functional compcache setup -- compcache is a virtual RAM boost (you know this, I'm just putting it out there for people not in the know/new to this discussion
). When your phone starts lagging do a simple test. Go into Running Services and check how much RAM you have in red that the phone can't access. That's the problem. On a full-sized PC/laptop there are far more options the system can use (but usually doesn't) to maximize RAM scalability and utility. Linux is MUCH better about it, particularly in low-RAM situations, than Windows does, but it still needs to clear the gunk out once in a while.
Think about what these phones are asked to do -- act as a 2-way radio with both WiFi/3G/1x and the CDMA voice system, plus browse the web, send SMS and MMS messages, play music, play Flash, take pictures, sense metal, search for ghosts (Ghost Radar on the Market by SpudPickles), handle a touch screen, etc. etc. etc. All of this with a meager 256MB of RAM, while running FroYo, and all at sub GHz speeds. A reboot every 24-36 hours doesn't seem like a lot to ask, especially at the sub 1-minute reboot time we have now.
Heck, mine will start dropping 3G, thanks to the mediocre coverage I have in my house, and I'll have to reboot just to fix the signal. That can happen up to 4 times a day, so I'm used to rebooting regularly anyway.