The Macbook has Infrared support, but its merely a receiver, much like that on your DVD player. IRDA, the infrared protocol for exchanging data is not implemented on the MacBook. IRDA has a number of security concerns associated with it, and is considered an archaic protocol these days, being replaced by wireless protocols, such as Wi-Fi and Bluetooth.
I wouldn't blame Apple for not have IRDA support - what you are asking is much the same as asking why your printer (which has a parallel port only) will not connect to your Dell Laptop, which only has USB. The simple answer is that one is much more advanced than the other. There are a lot of things that you don't find on laptops these days that were once there. 3 1/2 inch floppy? Serial/Paralell Ports? AA Batteries (heheh)
I suggest you get a new phone