It is more convenient than using the constructor because the only limited kind of expression is allowed in a base constructor call.
Also, the object initializer syntax can be used.
The equality operator is used to determine whether the next background
in the cycle should be loaded, to avoid pointless loads of the same
background several times (see #13362 and #13393). Its omission in the
latter pull caused seasonal backgrounds to no longer cycle.
Closes#13508.