Weather seal for unknown brand of window parts

I have 5 (five) 40" double hung (double tilt in) windows. We installed them new in late 90's, we think. The bottom sash on one window has a bubble seal on it. As near as I can figure, it is 58-156 for replacement. However, the other 4 windows do not have the side opening where you would slide the part in the slot on the window. Please see photos: IMG_1310 shows the windows without the opening to slide the weatherstripping. IMG_1308 is a cross-section of the weatherstrip
IMG_1307 shows the one window with the slot for weatherstrip. It almost looks like the window frame was burned to melt the material in order to open that slot up.
Since there are no openings on 4 of 5 windows, is it necessary to install any kind of weatherstrip?