Google Maps does not offer transit options in every country. When it does not have any knowledge about a city, at least it gives you an error message. In some places, such as Germany, it is worse. It tells you that the only option is take a train and walk the last 2 miles, because it does not know about the tram that has a stop right in front. (Interestingly, the map shows the tram stop, but I guess the schedule has not been added to the database.)
In addition, some apps let you quickly change max walking time (when carrying a heavy load), rule out the underground subway (when you want to take in the sights, rather than getting there quickly) or provide real time updates if the train is running late. Google Maps also lose the last address I've searched if I close the app and try to come back to it a little while later, ugh!... In any case, I just use a number of apps depending on my location and how well each tool serves my purpose at the time.
I can find the location in Apple's map, click on the transit button as before, and now I need to hit one extra icon to switch the app among the options it lists, so it is not painful at all. I'd rather Apple continues along with this type of service rather than provide a half baked in house transit option. Instead, it should focus on improving its POI database and search algorithm. That is a bigger deficiency in my opinion.