Also, has to be noted that costs for LG infrastructure it's same as the Habitat per Mpop, therefore, it is viable to use one or the other.
Except that population living in LG infrastructure will have smaller proportion available for manufacturing work than same population living in orbital hab.
You have to also note that population living on low G infrastructure planets produce LG infrastructure as a trade goods so will build it for free for itself and once those worlds are built up to their potential they will export it to other worlds for free too.
Since I play most of my games on a 0.33 tolerance to G for humans I can eventually use this to help me colonise new worlds and use the civilian fleets to grow new worlds quite effectively.
Using habitats is still very effective when you want strategically placed colonies. They can help if you are low on Corundium for regular mines rather than auto mines. I would not normally use Habitats for mining efforts unless there is some sort of shortage in Corundium first.
As pointed out Habitats give 100% worker output which is really helpful in some situations. Especially to exploit research bonuses, military colonies and outposts to use maintenance facilities, ordnance factories or just regular factories to produce some local resources. Maybe you want to use some really good administrator to build ships over Venus and place all your Military shipyards there.
There are MANY strategical reasons to use habitats.