Do UTXO's ever get consolidated to avoid complexitity? In 'Mastering Bitcoin' (pg 130) it is explained that a transaction will require higher fees if it is complex. For example, if I collect bitcoin from 100 people to buy a single tent, then when those 100 UTXO's (unspent transaction outputs) addressed to me will need to be aggregated by the miners when validating my purchase of the tent. This aggregation needs more kilobytes and is more complex so requires a larger fee. 

In the real world this would be like getting charged higher fees when paying with smaller coins. So do bitcoin transactions simply become more complex with time? What is there to consolidate UTXO'S and prevent them from being split down further and further making every transaction more complex in the long run?

Imagine if we could only get change, in the fiat world, but never consolidate it for larger notes. In the end we just all have pennies, right?

Where have I misunderstood?
When you pay someone using a number of utxo's to fund your payment, the output being created is a new single utxo with the total amount of all those input (minus change and fees).  Effectively, you are consolidating utxo's as inputs to fund your payment.

UTXO consolidation and breakage happens all the time by normal payments and doesn't usually require special intervention or handling by the user making the payment.