My house is 1300 sq feet, one story, The pipe from the washer would be a straight line from the washer through the kitchen to the two bathrooms. We have sewers. Why am I just now hearing it, I've lived here 46 years?

If your washer's water supply hose bursts, a drain pan, even a properly plumbed one, is not going to catch most of the water. I don't think these pans are of much use, except for a very slow leak that isn't spraying and possibly goes into the pan. I take two other precautions, though: 1) I have a battery powered leak alarm that sits on the floor of the laundry room and goes off if there is even a film of water on the floor, and 2) I shut off the supply valves when I am going on vacation. You can buy a leak alarm for about $10: Leak Alarm

I think you get it, but not sure, so in case you didn't know a tub drain (that also has a showerhead) is probably 1 1/2", and a washing machine needs 2". Also, you need a standpipe for the washer. So you really can't use any of the tub piping. Also, a floor drain requires a 2", so ditto. Not sure how the pipes run and where they tie into the main stack, but that may be what they are referring to by saying "cap" the tub piping. You can certainly put a floor drain in a Laundry Room. It can not be covered or restricted by an appliance. A pan under the washer has to have an air gap when draining into the floor drain. So, many people do not want to step on a floor drain or even see one at all, or see any pipe crawling along the floor from the pan to the drain, or see the pan itself, since Laundry Rooms now have 'chic' decoration (meaning "fashionable," not "chick"=female!). Also, most upper level Laundry Rooms do not have sloped floors, so you would need to pipe the pan or water is free to go anywhere, not just toward a potential floor drain. A pan is good peace of mind, it can catch problems with the machine tub itself. However, most problems occur with the hoses and connections, and those leaks most likely won't occur over the pan. So they make "flood safe" hoses that auto-shutoff when a leak is detected. There are other more complicated systems available as well. As another peace of mind, you can lay Schluter Ditra on the floor for waterproofing. Assuming with that you will have ceramic/porcelain, you can also slope the floor to a drain as well, and use a metal decorative grate instead of PVC. So many options, just plan ahead what you choose so the details can be worked out.

Most jurisdictions now require all of the effluent to go to the tank even though re-using the gray water for other purposes like irrigation would make a lot more sense.