... if a company makes a loss (i.e. its expenses exceeds its revenues) then they don't have to pay tax on their revenues...
The problem facing the ATO (and other countries' similar agencies) is that multi-national companies can (quite legitimately) manufacture expenses, for the express purpose of reducing their overall tax liability.
For example - a completely fictitious American company (which bares no resemblance to any real world company present or past), which we might call Giggle (let's say it's a mining company) has offices (operated by wholly owned subsidiaries in a complex ownership web) in Australia, Singapore and elsewhere where it does business.
Giggle Australia actually makes a large profit here from its Australian based operations, however it doesn't want to pay tax here - because Australia's company tax rate is 30%!
Giggle US decides that Giggle Singapore should hold all Intellectual Property rights (e.g. the right to use the “Giggle” TM and name) for operations in the Asia-Pacific region... And, it just so happens, that in Singapore - the corporate tax rate is around half that of Australia. So, quite reasonably, Giggle Global would rather pay tax in Singapore than in Australia, because it will make more overall profit that way.
So Giggle Singapore, the rightful owner of all Giggle IP in the region, decides that it will charge Giggle Australia a fee to use its IP. In a completely reasonable manner, it decides that this fee should be around the same amount as Giggle Australia makes in profit (before the fee is applied). So Giggle Singapore manufactures a (completely legal) expense, which Giggle Australia is forced to pay, which in turn effectively sends all Giggle Australia profits to Singapore.
Thus - Giggle Australia now pays no tax in Australia (where it would have paid 30%) but does pay tax on all that profit in Singapore (but only at half the rate which it would have paid in Australia). The Singapore government is very happy that such a low turnover operation as Giggle Singapore makes such a highh profit, and pays so much tax to them! The people of Australia are p!ssed off that Giggle Australia pays nothing back into the economy where it actually made the money in the first place!