Yes, it has to be designed like that. It is used for both recreational and competitive swimmers. Its primary function is to keep water out of the eyes to prevent any unclean materials enter your eyes to cause eye infection. And the water in swimming pool is cleaned by chemical liquid, which can make your eyes dry and red lead to eye irritation if your swimming goggles are not tight. On the other side, it enables a swimmer to see underwater to keep safety.
Actually, the potency dimension of swimming goggles should be moderate. Although the tight swimming goggles will prevent the water into the eyes which may make your eyes get infected, too tight potency dimension will make your eye nerves intense which may cause the dizziness. However, too lose is also not good, which may let the water in the swimming pool come into the eyes.
Buy goggles with formal brand in a nice shop or web. It is not necessary to make the goggle tight. It will make you very uncomfortable as your eyes are squeezed. Normal goggles shall have adjustable rubber strap and the tightness of the strap is irrelevant to the water-leaking. It is the rubber rings around the goggle lens that matters. If the rings are good, they may plying on your skin and protect your eyes from swimming water. So, buy goggles with formal brand and wear it comfortably.