This is mainly due to how long the delivery time is once the order is made. By ordering these materials at the proper time you ensure that they will be on the job when they are needed.
Some of the materials that need to be ordered with plenty of lead time include windows, plumbing fixtures, roofing, siding, electrical fixtures, brick, flooring, interior trim and appliances.
Windows and certain plumbing fixtures should be ordered about the time the foundation is poured. Windows can take 3 to 6 weeks to get so order them accordingly. Ideally you would like these ready for delivery once the roof is framed and covered with sheathing so they can be installed while the carpenter contractor is still there.
Plumbing fixtures such as bathtubs and shower stalls get put in place on the rough. Two to three weeks should be plenty of time to make this available for your plumber.
Roofing should also be ordered even if it is a stock item. wall mount kitchen faucet