I'm not sure exactly how to analyze the conditional constructions that English has, but it appears to have two: indicative conditionals and counterfactual conditionals.
If we analyze English this way, then counterfactual conditionals are more marked than indicative conditionals.
Example indicative conditional:
If the television is on downstairs, then someone turned it on
Example counterfactual conditional:
If I had eaten breakfast this morning, I would not be tired now.
I think counterfactual conditionals in English are reliably distinguished by the presence of the conditional mood in the consequent and specific verb tenses or possibly the subjunctive mood in the antecedent, but I'm not 100% sure that all counterfactual conditionals in English are actually marked.
I'm wondering whether there are any attested languages with fewer conditional constructions, i.e. no dedicated conditional constructions at all or no distinction between indicative and counterfactual conditionals, more conditional constructions (that are semantically distinct), or a very different inventory (such as counterfactual conditionals that are less marked than an alternative construction).