It is very common to have a "pad" module in modern I.C. design library. Besides including both input and output capable circuits there are ESD protection, Schmitt trigger configuration, output drive strength setting, pull-up or pull down resistor, edge polarity detection/latching for interrupt signalling, and voltage level shifting to provide higher voltage I/O capabililty from lower voltage inner core logic. The control lines for these functions are sometimes hard wired to fix a particular function or fed from a programmable latch that allows some of the functions to be changed by the programmer.
Even if all you need is a plain-old input it is easier to just use the library I/O module which in many cases incorporates the actual bonding pad for the IC. It also ensures a consistant, proven ESD and I/O performance to established standards which would be at risk of degenerating into a free-for-all if every designer was allowed to design their own I/O interface.