Gluten is a protein that gives bread elasticity. Water makes gluten spirals relax, and kneading helps stretch the gluten and connect with other gluten strands. Bread that lacks stretchiness:
- may not have enough gluten to start with. If you are using a low gluten flour then you won't get and elasticity. In general any plain white flour will have enough, but for best results use bread flour, also known as strong flour
- may be too dry. Gluten needs water to relax and stretch, if your dough is too dry, or "tight", then you won't get good elasticity
- may have not been worked enough or worked in the wrong way. Kneading mechanically stretches gluten, if it isn't kneaded enough, or the technique isn't right, then no elasticity
- may not have been risen enough. Yeast actually improves the dough, it really works on the gluten. Rise isn't just about leavening, it makes a big difference in elasticity. You should notice a big difference if it's been risen enough
If I had to put money on it I'd say it's probably your dough being too dry. This is an easy mistake to make, you turn your dough out on the counter and it's really gooey, must not have enough flour right? But as gluten get worked it uses up some of the extra moisture, so adding too much flour at the beginning will rob the gluten of the water it needs to relax. Kneading with oil instead of flour may help there.
As an aside, I generally add a couple of tablespoons of olive oil to my pizza dough to improve flavor and texture although that's totally optional. Also, you didn't list salt as an ingredient, bread needs some salt, many bakers recommend 10g per 500g of flour, although I usually cut that down some.