Yes, but...no. It depends. There are particular reasons to combine particular plants, and an herb such as basil growing next to a fruiter like tomatoes doesn't use the same minerals in great quantities.

That's one reason to interplant, but there are others, such as planting something as a pest repellant or trap. Naturtiums, for example, are loved by aphids, so the aphids will go to nasturtiums planted near other plants, and protect them. If all goes well, ladybug larvae will come in to feast on the hordes of aphids. Quite a sight to see!

There's a great book called "Carrots Love Tomatoes" that goes into this in great detail, specifically naming which plants to plant with which others, and why.

More reasons: weeds grow fast and multiply rapidly. They can intrude on seedling vegies and if tall, block sunlight. Best to keep them under control! Plus you learn about your soil.