This restricts bargaining by placing a hurdle at the end of the negotiations between parties. There are many parliamentary democracies without such investiture rules like the United Kingdom and most of the former British colonies, the Scandinavian countries and the Netherlands. Incentives for formation of oversized cabinets:

Oversized coalitions are particularly common in some countries, in which population consists of several distinct ethnic, linguistic or religious groups. Coalitions that involve all or almost all of the parliamentary parties are called grand coalitions and are especially common in wartime and other emergencies. They are typical for Switzerland in everyday politics as well.

1. William Riker’s reason for the formation of larger than minimal winning cabinets is the “information effect”: “If coalition-makers do not know how much weight a specific uncommitted participant adds, then they may be expected to aim at more than a minimum winning coalition.” This means that during the negotiations before the formation of a cabinet, there is uncertainty about how loyal the any of the future coalition members may be to the proposed cabinet. For this reason additional parties may be brought to the coalition “as insurance against defections and as guarantee for the cabinet’s winning status”.
2. Parties’ preferences are another reason for the enlargement of coalitions. Each party would prefer to have parties of equal weight on both of its sides. Coalition ABC is more attractive for B while C would prefer BCD, which brings the likeliness that an oversized coalition ABCD will be formed.
3. If the first priority objective of all or most of the parties is to defend the country or the democratic regime from external or internal threats. Churchill’s war cabinet in Britain is one of the examples of the grand coalitions that have frequently occurred in wartime. Internal threats are mainly any anti-democratic parties or movements. Ian Budge and Valentine Herman found that when a country is externally or internally threatened, in 72% of the cases such broad coalitions were formed.
4. Special majorities necessary for the amendments or regular legislation may be a strong reason for the emergence of oversized cabinets. If the new cabinet members intend to make important amendments to the constitution, any special majorities needed for achieving that will most probably broaden the coalition. An example of oversized cabinets is in Belgium during its constitutional reform, which led to the establishment of a new state in 1993.