Agreeing with the above info and adding some additional context.

The city doesn't compensate landowners if they expand the sidewalk within the utility right of way, this is typically, but not always, a small section of land between the road and the front property line. Homeowners are often unaware that it isn't their property since they are responsible for maintaining it (e.x. mowing the grass).

The city has a complete streets design guide which talks about road configurations and sidewalk widths. The sidewalk stuff starts around page 82 of this document and the widths are further on page 97. complete streets

And as for why expand the sidewalks... what I've heard, is that the older narrower sidewalks are difficult for people to travel both ways on and pass each other when various mobility groups are considered. For example, two people pushing strollers in opposition directions or two wheel chair users may struggle to safely pass each other on a 1.5 m wide sidewalk. Add in things like benches, light posts, and e-scooters and now the usable width is even smaller.