TPS depends a lot on how people use bitcoin. If they all use simple one signature 1 input 2 output transactions the TPS would be a lot higher than if they use complicated multi signature multi input  multi output transactions. The later is becoming more popular and taking up more space.
For example last block 672225 has only 1,657 transactions because it has a lot of txs that have more than 100 inputs up to 600, or output count of around 100. Which is why using TPS is a bad metric for bitcoin when you can pay 200 people in one tx.