Are designers allergic to cool designs or it's just harder to code?

So I'm a very beginner programmer, and I had an idea for a project. Every time I look at inspiration for UI I have been noticing this pattern of always having the same exact boring squares and shapes, which is far away from what I have planned, does this happen because people are just used to it and designers prefer something familiar or because it's actually too hard to code shapes that are not your typical basic shapes?