Changing the active Snap Mode from the Status Bar is not maintained during the placement of a line segment.
If you change the Snap Mode from the option available in the Status Bar this is only meant to be temporary. To make a permanent change during the operation of placing line segments etc. you need to double-click on the selected Snap on the Snap Mode tool. This is available under the menu item:
> Settings > Snaps > Button Bar
Use alternative snap mode while placing element