Sesquiplane. The Nieuport 17 and Albatross D.V being two famous and classic period examples from the opposing sides.

Tall Paul's opine doesn't rate much with me. I've seen how he stacks his car.'

Anyone who considers that they can ignore completely the reason most probable which is immediately obvious to experienced pilots in favour of some idealistic nonsense attributing it to development of aerodynamic design doesn't present as knowing anything worthwhile about flying, even less about human behaviour and the pragmatism behind all three aspects typically influencing the outcome of the subject under discussion.

As to the ability of the rounded structure being able to deflect the energy from a blow, and better still not to hang up on or rotate around upon striking an object including the poor ******* holding the wingtip - this has already been stated and is a prime example of why it offers optimum tip shape to minimise the catastrophic consequences of a tip strike resulting into a ground loop or worse. Of course aerodynamics or manufacture could have been an influence, but pilot survival rated a lot higher than aircraft longevity in terms of priority...and in an environment where attrition meant that machines were't designed like a Boeing to last in service for 20 years. You're not building a piece of furnitutre either. Though replacing machines was a logistical nightmare for the Germans, replacing pilots was even worse. Once that cadre of experience is gone, it becomes literally lambs to the slaughter! And I'm talking about the flying off and on the ground part, not engaging the enemy.