[usrusr]

Park+ride combines more of the drawbacks of personal vehicles and public transportation than robocab+ride would. (Initial sunk cost, always having to return to your personal vehicle instead of free roaming using whatever mode and path available, requiring the personal vehicle being operational at all times)

Also, robocab+ride could work on both ends of the commute. Where I live, "office suburbs" tend to have transit connections just as bad as actual suburbs, or worse.