Why to landlords evict or try to evict tenants from their apartments without a legal document for renovations and/or repairs?

This is too general a question and really cannot be answered unless you have a specific case. Landlords can perform emergency repair or schedule repairs but have to offer accommodations if a tenant has to vacate for a period of time.

My crystal ball is broken, but a specific question would be helpful.

General purpose and (in this case passive-aggressive) questions asking for rhetorical answers ("why" questions are generally rhetorical in nature) are more than challenging to answer - they are impossible. "Why" a given landlord does something is impossible for me - or any other attorney - to ascertain without knowing a great deal more information. We cannot speculate on another person's inner thoughts or motivations. What we CAN do is offer some information on how to respond to specific situations "My landlord locked me out and refused to accept my rent b/c I complained of bedbugs" is something I can help with. "Why do landlords...." is best left for a philosophy classroom.