The question here is not the whether or not the film scores of Morricone, Nyman, Glass, Williams, Shore, &c are classical music. Certainly the big scores you’re thinking about are symphonic & well within the purview of the modern symphony orchestras & choruses. (Yes, even Nyman. There is definitely a symphonic thinking in the way his music evolves, rather in the same way that the chamber music of Brahms is symphonic.)
If you want to argue over whether X Yz’s film scores are “classical” music, you may as well argue “classical” bona fides of many “popular classics” in the vein of André Rieu or the Arthur Fidler style pop-classics repertoire. All of this goes the problem with the word classical: it just doesn’t cut it as a word to describe orchestral/chamber/choral music outside popular styles!
<rant> Our language is so rich: why do we insist on propping up this anaemic, meaningless phrase “Classical Music” to describe any music at all? Even in technical usage one would be more likely to hear “music of the Classical Period” or “a classical symphony”, than the ill-defined word-pairing “classical music”. It’s now pretty much a just marketing term, & a bucket into which lazy people can toss anything from the Plainchant to the Viennese Classics to Popera & Chamber Pop — much like the equally vexed labels “alternative” & “indie”. As with most marketing misappropriations, the language is the poorer for it.
As to your supplementary question, Todd Wilcox answered that most succinctly with the observation that your “classical music” radio station will play what the market will buy: so if the target market wants Baroque & Rococo concerti, there's an almost inexhaustible supply of that repertoire for them to play. Equally, if the target market likes to hear arty or symphonic film scores, that’s what they’ll play.
I’m barely scratching the surface here. Your question touches on the purpose of the modern symphony orchestra: is it a museum of the canon or something alive & better? With the sunset of modernist though the light of the canon was dimmed & constellations of other works, worthy & unworthy, were revealed. Whose job is it to explore these? And on the subject of the quality of the music that modern art music ensembles should play, should they play all of the works of the “great composers”, or should we forego entirely, say, Wellington’s Victory or the Choral Fantasy & give air to a greater work from lesser-known, minority (e.g. female, non-European, not dead) composers?
The real question is not “Are orchestral movie soundtracks classical?”, but rather “Are these film scores art?” In answer to that one: it depends on the score.