- When people get something for free, they often don't value it as much and treat it worse. E.g. more pollution.
- public transportation being free also means that it will be used even in cases where it is both economically and ecologically a suboptimal solution. This is a problem because more usage means higher costs. E.g. someone now might take a bus instead of cycling.
- Less competition. This point is tricky, but essentially, other solutions such as private long-distance busses (which have a comparibly good ecological footprint) might go out of business. In general, market might develop suboptimal.
There are a lot of good points too, which makes it a difficult decision. But since you asked, those can be named as reasons I suppose.
On the con side:
- When people get something for free, they often don't value it as much and treat it worse. E.g. more pollution.
- public transportation being free also means that it will be used even in cases where it is both economically and ecologically a suboptimal solution. This is a problem because more usage means higher costs. E.g. someone now might take a bus instead of cycling.
- Less competition. This point is tricky, but essentially, other solutions such as private long-distance busses (which have a comparibly good ecological footprint) might go out of business. In general, market might develop suboptimal.
There are a lot of good points too, which makes it a difficult decision. But since you asked, those can be named as reasons I suppose.