Why can't they try? No one complains when Apple does it. I feel Apple should stick to hardware and OS but they branched out to many services like maps and music streaming, both duplicates of Google maps and Spotify.
But Apples services are the only ones that come pre-installed on your iOS device. They are not duplicated unless you choose to use alternative apps and install them additionally.
Samsung's duplicates are pre-installed additionally to the already better versions that come either baked into Android or mandatory installed according to their pre-requisite licensing with Google. That's the difference.
Adding insult to injury, you can then mostly only 'disable' these duplicates at best and can not properly uninstall them. Wasting resources on your device.
So Samsung are essentially spending resources on developing apps which will have to stand as duplicates on their devices because the Android licensing requires them to pre-install google's services. When Google's services are then better than the duplicate ones Samsung has developed, it makes you wonder and question why Samsung bother spending that resource in the first instance .... especially when development time and resources could be spent elsewhere.
Samples of duplication that come pre-installed on most Galaxy devices ...
1. Gallery - Samsung backup now supporting photos too.
2. Google Photos with photo backup
3. OneDrive (part of Microsoft deal) which likewise offers photos backup.
4. Google Docs / Sheets
5. Microsoft Office apps
6. Google Play Music
7. Samsung Music
8. Deezer / Spotify pre-installed in some regions
9. Samsung Game Centre
10. Google Games
11. Samsung Marketplace Store
12. Google Play
13. S-Voice
14. Google Now
And I could go on ....
Now add Bixby.