I read the following from a book titled "An Embedded Software Primer" by David E. Simon. (23rd print Nov/2014 – Page 16)
If no part on the circuit is driving a signal, then that signal is
said to be floating. Its voltage will be indeterminate and may change
as time passes. The results of a floating signal vary between harmless
and disastrous, depending upon how the parts with inputs connected to
the floating signal cope with the problem.
Based on this, it looks like there is no good reason why would a circuit have a floating signal. If this is right, then why would such signal be allowed?
Is this done due to a mistake in the board design?
Are there scenarios where such a signal is needed?