Without modifiers you end up with a menu listing 'Latte small', 'Latte medium', 'Latte large', 'Latte oat small' and so on — dozens of products that are really one product with choices. That bloat makes the till slow to use and the reports almost unreadable.
Modifier groups are usually configured with rules: single-choice or multi-select, mandatory or optional, and minimum and maximum selections. 'Pick exactly one size' is mandatory single-choice; 'add any toppings, up to three' is optional multi-select with a maximum.
Priced modifiers need care with costing. If extra cheese adds 5 QAR to the price it also adds real cost, and a system that does not account for that will overstate the margin on every modified sale.