If It Were So Easy
As a matter of fact the hodgepodge of business applications companies have grown over the years was done for a reason. Or more specifically, each application was developed, tested, introduced for a specific reason. The whole application landscape might look very ugly, but it resembles a serious investment that cannot easily be replaced or got rid of.
Just because the management idiots don't remember why these apps were introduced does not mean they are superfluous. Ask the grunts why these apps are there and you will discover that some ugly duck of app might me 100% mission critical for the company. The PHBs just don't know.
Sometimes that stuff can be replaced by SAP, Salesforce or other standard software, but typically people discover after the "transition" that some very critical, special business process cannot be done in that expensive "standard" solution. So the company has to bend over and adapt themselves to SAP's way of thinking or hire expensive SAP consultants to create - a new version of a custom application, based on SAP. What was the gain again ?