>>The technical reason is that we are supposed to minimize the time gap between making a blessing on food and eating it. So really when eating bread, we should have a slice cut and ready to eat before we make the blessing.<<
This is not 100% accurate. There is a din of shalem (whole) when making brachos. In cases where one can make a bracha on a whole item they should. If one has a pear which they will be slicing into pieces, they should make the bracha on the whole pear then slice off a piece and take a bite. Such an action is not considered a hefsek (a coconut would obviously be a hefsek, as would peeling an orange).
(This halacha was seen in the sefer V’zos HaBracha, and checked again by me prior to this post)
As such, on a loaf of bread, even during the week one should make their bracha on the whole loaf, then cut their slice.