Present simple or present continuous???

1. David isn't playing football today. He's injured his leg.

4. According to scientists, people are becoming taller and taller.

The other two are a bit more tricky as both are used. Always is to go with annoying habits apparently according to some grammar books but many English speakers would use the present tense then. So really if you want to emphasis that it's an annoying habit use the continuous. I'd say number 3 is continuous since the following sentence seems to show it's an annoying habit.  2 i think sounds better with the present.

2. Tina (always/complain) about having no money.
3. Rachel (always/plays) computer games. She never does her homework.