Indeed, the app is bad. That it exists or needs to exist is a bad thing. But given the Saudi government and Saudi law, the opinion of many women in Saudi Arabia is that scrapping the app would hurt their agency, not help it. They need male approval to travel either way, and by making it easier to get, the app, in practice, gives women more agency by lowering the bureaucratic barriers to travel.
The best way I can put it is that the app here doesn't really particularly help the oppressors. Like maybe, in a contrived way, you can argue that by making the oppression lighter weight you're less likely to have a full on revolution or something. But then, you've still lessened the oppression. That's not a bad thing.
But if removing the app from the store makes the experience of women in Saudi Arabia worse, which is exactly what many of those women are saying, then removing it doesn't do anything. You're just asking to have the Saudi society regress even further to a position where in practice women had even less agency.
Is that better?
[0]: https://twitter.com/monaeltahawy/status/1095360734798721025 an
[1]: http://time.com/5532221/absher-saudi-arabia-what-to-know/