Because Deliverables happens parallely. Both from Development side and testing side. Once the requirement is colllected developers build the product testers write the test cases according to the requirements. So Verfication and Validation Takes Place parallely so it is called V-Model
V stands for Verification and Validation.The shaped of the model is like bcz both development work and testers work starts and the same joins at one points and ends at the same time thats the reason this model is named as V-Model