Why don't juries have an odd number of jury members so there would be no jury deadlocks?

Criminal cases require unanimity on the verdict (in 48 of 50 US States and some Commonwealth countries) or a large (11-1, 10-2) majority (in certain N.Z. and Australia states for instance) so the jury having an odd or even number is irrelevant. Other countries have different rules, but again juries having and odd/even number have been dealt with by law. In Belguium for one example, a 6-6 vote results in a not guilty verdict, and 7-5 is referred to a panel of 3 judges whose vote, if unanimous, will reverse or affirm the judgement.
https://en.wikipedia.org/wiki/Juries#Trial_procedures

The U.S. Supreme Court has 9 justices at the moment, solving most tie possibilities (excepting abstentions).
The number of justices are fixed by Congress.
https://en.wikipedia.org/wiki/Supreme_Court_of_the_United_States#Size_of_the_Court

Noting that you're from Canada, Canada requires unanimity in criminal cases, so again the size of the jury is irrelevant in that regard.
https://en.wikipedia.org/wiki/Juries#Canada