The reference to modesty here is not about shyness and shame, but rather to the possibility of a proper and seemly approach to the bathroom, its size and appointments. These days, huge, luxurious bathrooms are touted by builders, by high-end plumbing-fixture companies, and in magazine articles. The room is supposed to include his-and-hers vanities, soaking tub and showerbath and indoor sauna, marble or onyx, and fixtures that are anything but the American standard.
If you live in an old house, however, you simply don’t have the room! And thus you have been spared the expense and constant cleaning those spa baths demand. You even may have grown to like your old bathroom. (I believe that a bathroom should be big enough for only one person at a time. How else can you get a break?) And you may have inherited the white tile, wainscot, capacious sink, clawfoot tub, linen closet, or old-fashioned medicine cabinet so coveted even in today’s mansion-size bathrooms.
A modest bathroom, dating to or modeled after those of the early 20th century, is probably in its original location. Such rooms are not perfectly preserved; their practical owners have fixed them up, painted them, added and deleted. The rooms are believable and functional because their owners responded to an existing bathroom (and presumably to what they knew about the house). Modest bathrooms are unique because limitation makes for creativity. They have “evolved,” with, say, a reproduction light joining a Forties radiator and Twenties tile. Such bathrooms have some quirks.