The phrase 'merely practical' is correct and usable in written English.
It can be used when referring to something or someone whose actions are driven by practicality rather than emotions. For example, "The candidate's decision to abandon the project was merely practical, rather than driven by sentimentality."
And as Bell points out, our wearable technologies have never been merely practical enhancements.
But travel guides offer more than merely practical help to get around unfamiliar cities.
From the other direction, stock examples of supposedly merely practical knowledge are acquired in apparently theoretical ways.
Such reasons will be "merely" practical, but reasons — reasons for reason, as it were — all the same.
Its direction is merely practical and competent, but the stage-managing of its complex events is remarkable.
Mr. Fessenden, 48, a staple of the New York underground scene as a writer, director, producer and actor, says his advice about "Stake Land" was merely practical.
And it is not merely symbolic, but practical, affecting lives and dreams.
That's why, I suspect, his metaphors have not merely poetic power but practical vitality, in the way that a horse is not only alive but usefully alive.
And my antipathy towards it wasn't merely philosophical and aesthetic, but practical: I learned from an early age that I'm a sort of inverse ET, killing flowers at touch.
It is not merely demonstrative, showing by example what styles of protest are tolerated (ineffectual ones, largely), but practical in the sense that it drastically foreshortens democratic possibilities.
But practical necessity is always the lever of creation; the line between practical necessity and aesthetic impulse is not merely fine but nonexistent.
