Why does the seven segment display have decimal point at the right?
Figure 1. Vertical display. Source.



Figure 2. Slanted display. Source.

Reasons for slant:


'7' in particular, '4' to a lesser extent and perhaps '2', '3', '5', '6' and '9' all appear more natural and resemble print typeface numerals more closely. The others look like italics which we are used to reading and the eye seems to accommodate this quite comfortably.


Reasons for decimal on the right:


There's more room there due to the slant. (See above.)
Decimal numbers &lt; 1 should always be written with a leading zero. The leading zero is a visual clue that a decimal is being displayed even if the observer doesn't notice it.


Personally, I find 'square' displays a little disconcerting.

Edit by Michael Karas

The idea to rotate one seven segment display 180° to create a colon for a clock, as posed in the comments, is just not a usable solution in my estimation. I have edited this here to be able to show why.