The house we just bought only has gutters in a couple of sections (usually where there is an exterior door). On one whole side, the have a "splash pad" of river rock on the ground where the runoff hits.

Are gutters necessary for the whole house?

Gutters are rarely "necessary". Though I would think if you have them, it is more aesthetically appealing to have them on the entire perimeter.

No. I very rarely put them on any house I build.

Either put gutters up or put rock beds where the water drains off the roof.

it seem that the higher end production builders in Houston are no longer putting gutters all around. They are using rock beds to disperse the runoff and perhaps short run gutters directly over doors.

Will be using gutters to capture rain water off certain roof pitches.

Where I live, they are mandated by code, due to expansive soil.

Your mileage may vary.

Ours were necessary. Our foundation is 110 years old, and when it rains, water would come through into our basement.

No company will touch our foundation since it's so old, but a structural engineer said it is still a sound foundation. They said they wouldnt even dig a foot or so to put a cement perimeter around the house.

Put up gutters and had downspouts run a few feet from the house to divert the water from the foundation. No leaks

I prefer them over entry ways, patios/porches (unless gabled), or any where I really need to control runoff.