In pushover analysis, why do we force the plastic hinge locations, such as indicating in our model instead of waiting for them to occur naturally? Also, do we usually need to show the spread of plasticity on a member in our model or it is too much academic?
The answer to this question varies by the application. In a working environment, it would take forever to model the connection accurately and incorporate it into a full building analysis. Run time would be to long and there would be so many things to model. Connection design and member design are handled in two different phases of the project's structural design and sometimes by different engineers (even by separate companies).
Typically, the spread of member plasticity is part of the connection design. You don't want your member to fail, you want the connection to fail. If a member fails it would need replacing and that's a lot more expensive than shoring the end of a beam and replacing its connection. This makes modeling the spread of member plasticity academic, as it's not utilized in the working environment.